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CDIAC - Atmosphere Glossary Category: Meteorology and astronomy > Atmosphere Date & country: 13/09/2007, USA Words: 301

dust veil inde
xA quantitative method developed by H. H. Lamb for comparing the magnitude of volcanic eruptions. The formulae use observations either of the depletion of the solar beam, temperature lowering in middle latitudes, or the quantity of solid matter dispersed as dust. The reference dust veil index is 1000, assigned to the Krakatoa 1883 eruption, and the index is calculated using all three methods, where the information is available, for statistical comparison purposes. Abbreviated D.V.I.

ecosystem
The interacting system of a biological community and its nonliving environmental surroundings.

eddy
A circular movement of water or air that is formed where currents pass obstructions or between two adjacent currents that are flowing counter to each other.

El Chicon
Active volcano 7300 ft (2225 m) high in Mexico. The last eruption was in 1983.

El Nino
An irregular variation of ocean current that from January to March flows off the west coast of South America, carrying warm, low-salinity, nutrient-poor water to the south. It does not usually extend farther than a few degrees south of the equator, but occasionally it does penetrate beyond 12 degrees S, displacing the relatively cold Peru Current. The effects of this phenomenon are generally short-lived, and fishing is only slightly disrupted. Occasionally (in 1891, 1925, 1941, 1957 - 58, 1965, …

emissions
Materials (gases, particles, vapors, chemical compounds, etc.) that come out of smokestacks, chimneys, and tailpipes.

emissivity
The ratio of the radiation emitted by a surface to that emitted by a black body at the same temperature.

energy balance models
An analytical technique to study the solar radiation incident on the Earth in which explicit calculations of atmospheric motions are omitted. In the zero- dimensional models, only the incoming and outgoing radiation is considered. The outgoing infrared radiation is a linear function of global mean surface air temperature, and the reflected solar radiation is dependent on the surface albedo. The albedo is a step function of the global meansurface air temperatures, and equilibrium temperatures are…

environment
The sum of all external conditions affecting the life, development, and survival of an organism.

epidemiology
The study of diseases as they affect populations, including the distribution of disease or other health-related states and events in human populations, the factors (e.g., age, sex, occupation, and economic status) that influence this distribution, and the application of this study to control health problems.

equilibrium line
The level on a glacier where accumulation equals ablation and the net balance equals zero.

estuary
Regions of interaction between rivers and near-shore ocean waters, where tidal action and river flow create a mixing of fresh and salt water.

euphotic zone
The layer of a body of water that receives sufficient sunlight for photosynthesis. The depth of this layer, which is about 80 m, is determined by the water's extinction coefficient, the cloudiness, and the sunlight's angle of incidence.

evapotranspiration
Discharge of water from the Earth's surface to the atmosphere by evaporation from bodies of water, or other surfaces, and by transpiration from plants.

feedback mechanisms
A sequence of interactions in which the final interaction influences the original one. Also see positive feedback and negative feedback.

fen
A type of wetland that accumulates peat deposits; they are less acidic than bogs, deriving most of their water from groundwater rich in calcium and magnesium.

firn
Material that is transitional between snow and glacier ice. It is formed from snow after passing through one summer melt season and becomes glacier ice after its permeability to liquid water falls to zero.

first detection
Identification of a precursor signal, detectable above the noise of natural climatic variability, of a significant change in a climate parameter and attribution of this change to an increase in atmospheric carbon dioxide concentration. The signal may be estimated by numeric modeling of the climate, and the noise can be estimated using instrumental data. For any modeled signal that is estimated, the corresponding noise can be estimated from observational data, and a signal-to-noise ratio can be c…

flaring
The burning of waste gases through a flare stack or other device before releasing them to the air.

flow law
In glaciology, a constitutive relation for the analysis of three-dimensional deformation states of ice subjected to stress.

fog
Liquid particles less than 40 microns in diameter that are formed by condensation of vapor in air.

food chain
A sequence of organisms, each of which uses the next lower member of the sequence as a food source.

fossil fuel
Any hydrocarbon deposit that can be burned for heat or power, such as petroleum, coal, and natural gas.

fungi
Molds, mildews, yeasts, mushrooms, and puffballs, a group of organisms that lack chlorophyll and therefore are not photosynthetic. They are usually nonmobile, filamentous, and multicellular.

general circulation models
Hydrodynamic models of the atmosphere on a grid or spectral resolution that determine the surface pressure and the vertical distributions of velocity, temperature, density, and water vapor as functions of time from the mass conservation and hydrostatic laws, the first law of thermodynamics, Newton's second law of motion, the equation of state, and the conservation law for water vapor. Abbreviated as GCM. Atmospheric general circulation models are abbreviated AGCM, while oceanic general circulati…

geomorphology
The study of present-day landforms, including their classification, description, nature, origin, development, and relationships to underlying structures. Also the his- tory of geologic changes as recorded by these surface features. The term is sometimes restricted to features produced only by erosion and deposition.

geosphere
The solid mass (lithosphere) of the Earth as distinct from the atmosphere and hydrosphere or all three of these layers combined.

geostrophic flow
A type of movement where the Coriolis force balances exactly the horizontal pressure force.

glacial maximum
The position or time of the greatest advance of a glacier (e.g., the greatest equatorward advance of Pleistocene glaciation).

glacial rebound
The isostatic adjustment of previously glaciated areas after glacial retreat (e.g., the uplift of Scandinavia after the most recent glaciation).

glacier
A mass of land ice that is formed by the cumulative recrystallization of firn. A glacier flows slowly (at present or in the past) from an accumulation area to an ablation area. Some well-known glaciers are: the Zermatt, Stechelberg, Grindelwald, Trient, Les Diablerets, and Rhone in Switzerland; the Nigards, Gaupne, Fanarak, Lom, and Bover in Norway; the Wright, Taylor, and Wilson Piedmont glaciers in Antarctica; the Bossons Glacier in France; the Emmons and Nisqually glaciers on Mt. Ranier, Wash…

glacier flow (ice flow).
The slow downward or outward movement of ice in a glacier caused by gravity.

greenhouse effect
A popular term used to describe the roles of water vapor, carbon dioxide, and other trace gases in keeping the Earth's surface warmer than it would be otherwise. These ' radiatively active ' gases are relatively transparent to incoming shortwave radiation, but are relatively opaque to outgoing longwave radiation. The latter radiation, which would otherwise escape to space, is trapped by these gases within the lower levels of the atmosphere. The subsequent reradiation of some of the energy back t…

greenhouse gases
Those gases, such as water vapor, carbon dioxide, tropospheric ozone, nitrous oxide, and methane, that are transparent to solar radiation but opaque to longwave radiation. Their action is similar to that of glass in a greenhouse. Also see greenhouse effect and trace gas.

Greenland Ice Sheet
See ice sheet.

grenz
A soil horizon, which is frequently marked by a bed of clay, that results from a temporary halt in the accumulation of vegetal material.

gross primary production
The total amount or weight of organic matter created by photosynthesis over a defined time period (total product of photosynthesis). Abbreviated GPP.

ground cover
Plants grown to keep soil from eroding.

grounding line
The boundary between the area where an ice shelf or a glacier is floating on water and where it is in contact with the shore or underlying earth (grounded).

groundwater
The supply of fresh water found beneath the surface of the Earth (usually in aquifers) that often supplies wells and springs.

growth water-use efficiency
A measure at the individual plant level of how well plants use available water in growth. The units of dry matter synthesized are divided by the units of water lost.

Gulf Stream meander
A transient winding bend in the Gulf Stream. These bends intensify as the Gulf Stream merges into the North Atlantic and can break up into detached eddies at about 40 degrees S.

gyres
Major circular flow patterns in the oceans. The wind- driven eastward- and westward-flowing equatorial currents are blocked by the continents and rotate slowly in a clockwise direction in the North Atlantic and Pacific Oceans and in a counter- clockwise direction in the South Atlantic, South Pacific, and Indian Oceans.

Hadley cell
A direct thermally-driven and zonally symmetric large- scale atmospheric circulation first proposed by George Hadley in 1735 as an explanation for the trade winds. It carries momentum, sensible heat, and potential heat from the tropics to the mid-latitudes (30 degrees). The poleward transport aloft is complemented by subsidence in the subtropical high pressure ridge and a surface return flow. The variability of this cell and the Walker cell is hypothesized to be a major factor in short-term clim…

halocline
In the oceans, a well-defined vertical gradient of salinity.

heat flux (thermal flux)
The amount of heat that is transferred across a surface of unit area in a unit of time.

heat island effect
A dome of elevated temperatures over an urban area caused by the heat absorbed by structures and pavement.

herbivore
An animal that feeds on plants.

heterotrophs
Organisms that break down and use organic matter.

histosol
Wet organic soils, such as peats and mucks.

Holdridge life zone
A climate category defined by three weighted climatic indexes, namely, mean annual heat, precipitation, and atmospheric moisture.

Holocene
The most recent epoch of the Quaternary period , covering approximately the last 10,000 years.

humus
Decomposed organic material.

hydrologic budget
A quantitative accounting of all water volumes and their changes with time for a basin or area.

hydrologic cycle
The process of evaporation, vertical and horizontal transport of vapor, condensation, precipitation, and the flow of water from continents to oceans. It is a major factor in determining climate through its influence on surface vegetation, the clouds, snow and ice, and soil moisture. The hydrologic cycle is responsible for 25 to 30 percent of the mid-latitudes' heat transport from the equatorial to polar regions.

hydrology
The science dealing with the properties, distribution, and circulation of water.

hydrosphere
The aqueous envelope of the Earth, including the oceans, freshwater lakes, rivers, saline lakes and inland seas, soil moisture and vadose water, groundwaters, and atmospheric vapor.

hydrostatic equation
In the vector equation of motion, the form assumed by the vertical component when all Coriolis, earth-curvature, frictional, and vertical-acceleration terms are con- sidered negligible compared with those involving the vertical pressure force and the force of gravity. The error in applying the hydrostatic equation to the atmosphere for cyclonic-scale motions is less than 0.01%. In extreme situations, the strong vertical accelerations in thunderstorms and mountain waves can be 1% of gravity.

hypsithermal period
The period about 4000 to 8000 years ago when the Earth was apparently several degrees warmer than it is now. More rainfall occurred in most of the subtropical desert regions and less in the central midwest United States and Scandinavia. It is also called the altithermal period and can serve as a past climate analog for predicting the regional pattern of climate change should the mean Earth surface temperature increase from an increase in atmospheric carbon dioxide concentration.

ice age
A glacial epoch or time of extensive glacial activity. Also, as Ice Age, which refers to the latest glacial epoch, the Pleistocene Epoch.

ice and snow albedo
The reflectivity of ice and snow-covered surfaces. The albedo of freshly fallen snow may be as much as 90%, while older snow may have values of 75% or less. The larger the areal extent of snow and ice cover, the higher the albedo value. The surface albedo will also increase as a function of the depth of snow cover up to 13 cm and be unaffected by increased snow cover after reaching that depth.

ice cover
During the present time, the extent, especially the thickness, of glacier ice on a land surface. Also the same as ice concentration, which is the ratio of an area of sea ice to the total area of sea surface within some large geographic area.

ice flow
See glacier flow.

ice front
The floating vertical cliff that forms the seaward face or edge of a glacier or an ice shelf that enters water. It can vary from 2 to 50 m in height.

ice sheet (continental glacier)
A glacier of considerable thickness and more than 50,000 sq km in area. It forms a continuous cover of ice and snow over a land surface. An ice sheet is not confined by the underlying topography but spreads outward in all directions. During the Pleistocene Epoch, ice sheets covered large parts of North America and northern Europe but they are now confined to polar regions (e.g., Greenland and Antarctica).

ice shelf
A sheet of very thick ice with a level or gently undulating surface. It is attached to the land on one side, but most of it is floating. On the seaward side, it is bounded by a steep cliff (ice front) 2 to 50 m or more above sea level. Ice shelves have formed along polar coasts (e.g., Antarctica and Greenland); they are very wide with some extending several hundreds of kilometers toward the sea from the coastline. They increase in size from annual snow accumulation and seaward extension of land …

infiltration (soil)
Movement of water from the ground surface into the soil.

infrared radiation
Electromagnetic radiation lying in the wavelength interval from 0.7 micrometers to 1000 micrometersm. Its lower limit is bounded by visible radiation, and its upper limit by microwave radiation. Most of the energy emitted by the Earth and its atmosphere is at infrared wavelength. Infrared radiation is generated almost entirely by large-scale intra- molecular processes. The tri-atomic gases, such as water vapor, carbon dioxide, and ozone, absorb infrared radiation and play important roles in the …

insolation
The solar radiation incident on a unit horizontal surface at the top of the atmosphere. It is sometimes referred to as solar irradiance. The latitudinal variation of insolation supplies the energy for the general circulation of the atmosphere. Insolation depends on the angle of incidence of the solar beam and on the solar constant.

inversion
An anomaly in the normal positive lapse rate; usually refers to a thermal inversion, in which temperature increases rather than decreases with height.

irradiance
The total radiant flux received on a unit area of a given real or imaginary surface. Also called the radiant flux density.

isopynic
A line on a chart that connects all points of equal or constant density.

isotherm
A line on a chart that connects all points of equal or constant temperature.

isotope
One of two or more atoms that have the same atomic number (i.e., the same number of protons in their nuclei) but have different mass numbers.

Krakatoa (Krakatau)
Active volcano 2667 ft (813 m) high in West Indonesia. It forms an island between Java and Sumatra. Its eruption in 1883, which was one of the most violent in modern times, scattered debris and darkened skies over vast areas. Additional eruptions occurred in late 1927 and in the l960s.

lapse rate
The rapidity with which temperature decreases with altitude. The normal lapse rate is defined to be 3.6 degrees F per 1000 feet change in altitude. The dry adiabatic lapse rate is about 5.5 degrees F per 1000 feet, and the wet adiabatic lapse rate varies between 2 and 5 degrees F per 1000 feet.

latent heat
Energy transferred from the earth's surface to the atmosphere through the evaporation and condensation processes.

Le Chatelier's principle
When an external force is applied to an equilibrium system, the system adjusts to minimize the effect of the force.

life zone
A climatically-defined class that can be associated with regions of soil and biota with a high uniformity in species composition and environmental adaptation. See Holdridge life zone.

lithosphere
The component of the Earth's surface comprising the rock, soil, and sediments. It is a relatively passive component of the climate system, and its physical character- istics are treated as fixed elements in the determination of climate.

litter
Undecomposed plant residues on the soil surface.

Little Ice Age
A cold period that lasted from about A.D. 1550 to about A.D. 1850 in Europe, North America, and Asia. This period was marked by rapid expansion of mountain glaciers, especially in the Alps, Norway, Ireland, and Alaska. There were three maxima, beginning about 1650, about 1770, and 1850, each separated by slight warming intervals.

loess
A buff-colored, wind-blown deposit of fine silt, which is frequently exposed in bluffs with steep faces. The thickness can range from 6 to 30 m. The loess of the USA and Europe is thought to be the fine materials first transported and deposited by the waters of melting ice sheets during the glacial period. It was later blown consider- able distances with, in some cases, deposition in lakes. The origin of Asiatic loess, however, is apparently wind-blown dust from central Asian deserts.

longwave radiation
The radiation emitted in the spectral wavelength greater than 4 micrometers corresponding to the radiation emitted from the Earth and atmosphere. It is sometimes referred to as terrestrial radiation or infrared radiation, although somewhat imprecisely.

marsh
A type of wetland that does not accumulate appreciable peat deposits and is dominated by herbacious vegetation. Marshes may be fresh- or saltwater, tidal or nontidal.

mass balance
The application of the principle of the conservation of matter. For example, the mass of a glacier is not destroyed or created; the mass of a glacier and all its constitutive components remains the same despite alterations in their physical states. The mass balance of a glacier is calculated with the input/output relationships of ice, firn, and snow, usually measured in water equivalent. Output includes all ablative processes of surface melting, basal melting, evaporation, wind deflation, calvin…

Mauna Loa
An intermittently active volcano 13,680 ft (4,170 m) high in Hawaii. Last eruption was in 1984. Also see Mauna Loa record.

Mauna Loa record
The record of measurements of atmospheric carbon dioxide concentrations taken at the Mauna Loa Observatory, Mauna Loa, Hawaii, since March 1958. The Mauna Loa record is the longest reliable daily record of atmospheric carbon dioxide measurements in the world.

Maunder minimum
The period from 1654 to 1714 when it was believed that there were no sunspots. It is now thought that there were some sunspots during that time but less than the numbers counted after 1800.

mean sea level
The average height of the sea surface, based upon hourly observation of the tide height on the open coast or in adjacent waters that have free access to the sea. In the United States, it is defined as the average height of the sea surface for all stages of the tide over a nineteen year period. Mean sea level, commonly abbreviated as MSL and referred to simply as sea level, serves as the reference surface for all altitudes in upper atmospheric studies.

mesic environment
A habitat with a moderate amount of water.

mesoscale eddies (mode eddies)
In the ocean, dense and irregularly-oval high- and low- pressure centers about 400 km in diameter. The intensities of currents in these centers are about 10 times greater than the local means.

Milankovitch theory
An astronomical theory formulated by the Yugoslav mathematician Milutin Milankovitch that associates climate change with fluctuations in the seasonal and geographic distribution of insolation determined by periodic variations of the Earth's eccentricity and obliquity and the longitude of the perihelion.

mist
Liquid particles 40 to 500 microns in diameter that are formed by condensation of vapor in air.

modeling
An investigative technique that uses a mathematical or physical representation of a system or theory that accounts for all or some of its known properties. Models are often used to test the effects of changes of system components on the overall performance of the system.

monsoon
A name for seasonal winds, first applied to the winds over the Arabian Sea that blow for six months from the northeast and for six months from the southwest. The term has been extended to similar winds in other parts of the world (i.e., the prevailing west to northwest winds of summer in Europe have been called the European monsoon). The primary cause for these seasonal winds is the much greater annual variation of temperature over large land areas compared with neighboring ocean surfaces, causi…

natural selection
The process of survival of the fittest by which organisms that adapt to their environment survive while those that do not adapt disappear.

negative feedback
An interaction that reduces or dampens the response of the system in which it is incorporated.

net primary production
The part of the gross primary production that remains stored in the producer organism (primarily green plants) after deducting the amount used during the process of respiration. Abbreviated NPP.

nutrient
Any substance assimilated by living things that promotes growth.