|A| B | C | D| E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z |
Wednesday
W, X, Y, Z
W
wake stream theory [OCEANOGR] The theory that, in a stratified ocean, a compensation
current must develop on the right side of a wake stream, flowing in the same direction,
and a countercurrent in the opposite direction must appear to the left.
wall reef [GEOL] A linear, steep-sided coral reef constructed on a reef wall.
wall-sided glacier [HYD] A glacier unconfined by a marked ravine or valley.
wandering water See vadose water.warm-air drop See warm pool.
warm air mass [METEOROL] An air mass that is warmer than the surrounding air; an
implication that the air mass is warmer than the surface over which it is moving.
warm anticyclone See warm high.
warm-blooded See homoiothermal.
warm-core anticyclone See warm high.
warm-core cyclone See warm low.
warm-core high See warm high.
warm-core low See warm low.
warm cyclone See warm low.
warm drop See warm pool.
warm front [METEOROL] Any nonoccluded front, or portion thereof, which moves in
such a way that warmer air replaces colder air.
warm high [METEOROL] At a given level in the atmosphere, any high that is warmer at its
center than at its periphery. Also known as warm anticyclone; warm-core anticyclone; warm-core high.
warm low [METEOROL] At a given level in the atmosphere, any low that is warmer at
its center than at its periphery; the opposite of a cold low. Also known as warm-core
cyclone; warm-core low; warm cyclone.
warm pool [METEOROL] A region, or pool, of relatively warm air surrounded by colder
air; the opposite of a cold pool; commonly applied to warm air of appreciable vertical
extent isolated in high latitudes when a cutoff high is formed. Also known as warm-air
drop; warm drop.
warm sector [METEOROL] The area of warm air, within the circulation of a wave cyclone,
which lies between the cold front and warm front of a storm.
warm tongue [METEOROL] A pronounced poleward extension or protrusion of warm
air.
warm-tongue steering
warm-tongue steering [METEOROL] The steering influence apparently exerted upon a
tropical cyclone by an upper-level warm tongue which often extends a considerable
distance into regions adjacent to the cyclone.
warm wave See heat wave.
warning stage [HYD] The stage, on a fixed river gage, at which it is necessary to begin
issuing warnings or river forecasts if adequate precautionary measures are to be taken
before flood stage is reached.
wash-and-strain ice foot [OCEANOGR] An ice foot formed from ice casts and slush and
attached to a shelving beach, between the high and low waterlines; high waves and
spray may cause it to build up above the high waterline.
wasp [ZOO] The common name for members of 67 families of the order Hymenoptera;
all are important as parasites or predators of injurious pests.
waste pipe [CIV ENG] Apipe to carry waste water from a basin, bath, or sink in a building.
waste plain See alluvial plain.
waste vent See stack vent.
water atmosphere [METEOROL] The concept of a separate atmosphere composed only
of water vapor.
water-bearing strata [GEOL] Ground layers below the standing water level.
water-borne [SCI TECH] Floating on or transported by water.
water budget See hydrologic accounting.
water cloud [METEOROL] Any cloud composed entirely of liquid water drops; to be
distinguished from an ice-crystal cloud and from a mixed cloud.
water conservation [ECOL] The protection, development, and efficient management
of water resources for beneficial purposes.
water content [HYD] The liquid water present within a sample of snow (or soil) usually
expressed in percent by weight; the water content in percent of water equivalent is
100 minus the quality of snow. Also known as free-water content; liquid-water content.
X
xanthan gum [BIOL] A polysaccharide produced by the bacterium Xanthomonas campestris that is used as a thickener and stabilizer in foods; also used in oil recovery to help improve water flooding and oil displacement.
xanthene [CHEM] CH2 (C6H4)2O Yellowish crystals that are soluble in ether, slightly soluble in water and alcohol; melts at 100˚C; used as a fungicide and chemical intermediate. Also known as tricyclic dibenzopyran.
9-xanthenone See genicide.
Xanthomonas citri [MICROBIO] The bacterial pathogen that causes citrus canker.
xanthone [CHEM] CO(C6H4)2O White needle crystals that are found in some plant pigments; insoluble in water, soluble in alcohol, chloroform, and benzene; melts at 173˚C, sublimes at 350˚C; used as a larvicide, as a dye intermediate, and in perfumes and pharmaceuticals.
xenogamy [BOT] Cross-fertilization between flowers on different plants.
xenon [CHEM] An element, symbol Xe, member of the noble gas family, group 0, atomic number 54, atomic weight 131.291; colorless, boiling point −108˚C (1 atmosphere, or 101,325 pascals), noncombustible, nontoxic, and nonreactive; used in photographic flash lamps, luminescent tubes, and lasers, and as an anesthetic.
xerarch succession [ECOL] A type of succession that originates in a dry habitat
xeric [ECOL] 1. Of or pertaining to a habitat having a low or inadequate supply of moisture. 2. Of or pertaining to an organism living in such an environment
xeromorphic [ECOL] Referring to a plant that is able to survive in dry environments.
xerophyte [ECOL] A plant adapted to life in areas where the water supply is limited.
xerosere [ECOL] A temporary community in an ecological succession on dry, sterile ground such as rock, sand, or clay.
xerothermic [CLIMATOL] Characterized by dryness and heat.
xerotolerance [BIOL] The ability to grow in extremely dry habitats.
xylem [BOT] The principal water-conducting tissue and the chief supporting tissue of higher plants; composed of tracheids, vessel members, fibers, and parenchyma.
xylene [CHEM] C6H4(CH3)2 Any one of the family of isomeric, colorless aromatic hydrocarbon liquids, produced by the destructive distillation of coal or by the catalytic reforming of petroleum naphthenic fractions; used for high-octane and aviation gasolines, solvents, chemical intermediates, and the manufacture of polyester resins. Also known as dimethylbenzene; xylol.
ortho-xylene [CHEM] 1,2-C6H4(CH3)2 A flammable, moderately toxic liquid; insoluble in water, soluble in alcohol and ether; boils at 144˚C; used to make phthalic anhydride, vitamins, pharmaceuticals, and dyes, and in insecticides and motor fuels.
xylenol [CHEM] (CH3)2C6H3OH Highly toxic, combustible crystals; slightly soluble in water, soluble in most organic solvents; melts at 20–76˚C; used as a chemical intermediate, disinfectant, solvent, and fungicide, and for pharmaceuticals and dyestuffs.
xylol See xylene.
xylophagous [BIOL] Referring to an organism which feeds on wood.
Y
yaws [MED] An infectious tropical disease of humans caused by the spirochete
Treponema pertenue; manifested by a primary cutaneous lesion followed by a
granulomatous skin eruption.
yeast [MYCOL] A collective name for those fungi which possess, under normal
conditions of growth, a vegetative body (thallus) consisting, at least in part, of simple, individual cells.
yellow dwarf [PL PATH] Any of several plant viral diseases characterized by yellowing of the foliage and stunting of the plant.
yellow-green algae [BOT] The common name for members of the class Xanthophyceae.
yellow phosphorus See white phosphorus.
yellows [PL PATH] Any of various fungus diseases of plants characterized by yellowing of the leaves which later turn brown, become brittle, and die; affects cabbage, lettuce, cauliflower, peach, sugarbeet, and other plants.
Yellow Sea [GEOGR] An inlet of the Pacific Ocean between northeastern China and Korea.
yellow snow [HYD] Snow with a golden or yellow appearance because of the presence of pine or cypress pollen.
young ice [HYD] Newly formed ice in the transitional stage of development from ice crust to winter ice.
Yucat´an Current [OCEANOGR] A rapid northward flowing current along the western side of the Yucatｴan Strait; generally loops to the north and exits as the Florida Current.
Z
zastruga See sastruga.
Zeitgeber [BIOL] A periodic environmental condition or event that acts to set or reset an innate biological rhythm of an organism.
zenithal rain [METEOROL] In the tropics or subtropics, the rainy season which recurs annually or semiannually at about the time that the sun is most nearly overhead (at zenith).
zephyr [METEOROL] Any soft, gentle breeze.
zero layer [OCEANOGR] A reference level in the ocean, at which horizontal motion is at a minimum.
zero population growth [ECOL] Situation in which each organism in a population is replaced by only one offspring, so there is no increase in population size.
zinc arsenite [CHEM] Zn(AsO2)2 A toxic white powder that is insoluble in water, soluble in alkalies; used as an insecticide and timber preservative. Also known as zinc metaarsenite.
zinc chloride [CHEM] ZnCl2 Water- and alcohol-soluble, white, fire-hazardous crystals that melt at 290˚C, and are irritating to the skin; used as a catalyst and in electroplating, wood preservation, textile processing, petroleum refining, medicine, and feed additives.
zinc metaarsenite See zinc arsenite.
zinc naphthenate [CHEM] Zn(C6H5COO)2 A combustible, viscous, acetone-soluble solid; used in paints, varnishes, and resins, and as a drier and wetting agent, insecticide, fungicide, and mildewstat.
zinc orthoarsenate [CHEM] Zn3 (AsO4)2 A toxic white powder that is insoluble in water, soluble in alkalies; used as an insecticide and wood preservative.
zinc sulfate [CHEM] ZnSO4ｷ7H2O Efflorescent, water-soluble, colorless crystals with an astringent taste; used to preserve skins and wood and as a paper bleach, analytical reagent, feed additive, and fungicide. Also known as white copperas; white vitriol; zinc vitriol.
zinc sulfide [CHEM] ZnS A yellowish powder that is insoluble in water, soluble in acids; exists in two crystalline forms (alpha, or wurtzite, and beta, or sphalerite); beta becomes alpha at 1020˚C, and sublimes at 1180˚C; used as a pigment for paints and linoleum, in opaque glass, rubber, and plastics, for hydrosulfite dyeing process, as x-ray and television screen phosphor, and as a fungicide.
zinc vitriol See zinc sulfate.
zonal [METEOROL] Latitudinal, easterly or westerly, opposed to meridional.
zonal circulation See zonal flow.
zonal flow [METEOROL] The flow of air along a latitude circle; more specifically, the latitudinal (east or west) component of existing flow. Also known as zonal circulation.
zonal index [METEOROL] A measure of strength of the middle-latitude westerlies, expressed as the horizontal pressure difference between 35˚and 55˚latitude, or as the corresponding geostrophic wind.
zonal kinetic energy [METEOROL] The kinetic energy of the mean zonal wind, obtained by averaging the zonal component of the wind along a fixed latitude circle.
zonal soil [GEOL] In early classification systems in the United States, a soil order including soils with well-developed characteristics that reflect the influence of agents of soil genesis. Also known as mature soil.
zonal westerlies See westerlies.
zonal wind [METEOROL] The wind, or wind component, along the local parallel of latitude, as distinguished from the meridional wind.
zonal winds See westerlies.
zonal wind-speed profile [METEOROL] A diagram in which the speed of the zonal flow is one coordinate and latitude the other.
zonation [ECOL] Arrangement of organisms in biogeographic zones.
zone [GEOGR] An area or region of latitudinal character. [GEOL] A belt, layer, band, or strip of earth material such as rock or soil.
zone of accumulation See B horizon.
zone of aeration [GEOL] The subsurface sediment above the water table containing air and water. Also known as unsaturated zone; vadose zone; zone of suspended water.
zone of illuviation See B horizon.
zone of maximum precipitation [METEOROL] In a mountain region, the belt of elevation at which the annual precipitation is greatest.
zone of saturation [HYD] A subsurface zone in which water fills the interstices in soil and is under pressure greater than atmospheric pressure; the top of the zone of saturation marks the water table for the area. Also known as phreatic zone; saturated zone.
zone of soil water See belt of soil water.
zone of suspended water See zone of aeration.
zoocecidium [PL PATH] A plant gall usually caused by an insect.
zoochlorellae [BIOL] Unicellular green algae which live as symbionts in the cytoplasm of certain protozoans, sponges, and other invertebrates.
zoochory [BOT] Dispersal of plant disseminules by animals.
zoogeographic region [ECOL] A major unit of the earth’s surface characterized by faunal homogeneity.
zoogeography [BIOL] The science that attempts to describe and explain the distribution of animals in space and time.
zoology [BIOL] The science that deals with knowledge of animal life.
zoonoses [BIOL] Diseases which are biologically adapted to and normally found in lower animals but which under some conditions also infect humans.
zooplankton [ECOL] Microscopic animals which move passively in aquatic ecosystems.
zoosphere [ECOL] The world community of animals.
zoosporangium [BOT] A spore case bearing zoospores.
zootoxin [BIOL] A toxic substance or poison produced by an animal, for example, snake venom.
zooxanthellae [BIOL] Microscopic yellow-green algae which live symbiotically in certain radiolarians and marine invertebrates.
zoster See herpes zoster.
zygospore [BOT] A thick-walled cell or resting spore that results from the fusion of similar reproductive cells, especially in organisms that reproduce by conjugation.
zymosis See fermentation.
Zythiaceae [MYCOL] A family of fungi of the order Sphaeropsidales which contains many plant and insect pathogens.
wake stream theory [OCEANOGR] The theory that, in a stratified ocean, a compensation
current must develop on the right side of a wake stream, flowing in the same direction,
and a countercurrent in the opposite direction must appear to the left.
wall reef [GEOL] A linear, steep-sided coral reef constructed on a reef wall.
wall-sided glacier [HYD] A glacier unconfined by a marked ravine or valley.
wandering water See vadose water.warm-air drop See warm pool.
warm air mass [METEOROL] An air mass that is warmer than the surrounding air; an
implication that the air mass is warmer than the surface over which it is moving.
warm anticyclone See warm high.
warm-blooded See homoiothermal.
warm-core anticyclone See warm high.
warm-core cyclone See warm low.
warm-core high See warm high.
warm-core low See warm low.
warm cyclone See warm low.
warm drop See warm pool.
warm front [METEOROL] Any nonoccluded front, or portion thereof, which moves in
such a way that warmer air replaces colder air.
warm high [METEOROL] At a given level in the atmosphere, any high that is warmer at its
center than at its periphery. Also known as warm anticyclone; warm-core anticyclone; warm-core high.
warm low [METEOROL] At a given level in the atmosphere, any low that is warmer at
its center than at its periphery; the opposite of a cold low. Also known as warm-core
cyclone; warm-core low; warm cyclone.
warm pool [METEOROL] A region, or pool, of relatively warm air surrounded by colder
air; the opposite of a cold pool; commonly applied to warm air of appreciable vertical
extent isolated in high latitudes when a cutoff high is formed. Also known as warm-air
drop; warm drop.
warm sector [METEOROL] The area of warm air, within the circulation of a wave cyclone,
which lies between the cold front and warm front of a storm.
warm tongue [METEOROL] A pronounced poleward extension or protrusion of warm
air.
warm-tongue steering
warm-tongue steering [METEOROL] The steering influence apparently exerted upon a
tropical cyclone by an upper-level warm tongue which often extends a considerable
distance into regions adjacent to the cyclone.
warm wave See heat wave.
warning stage [HYD] The stage, on a fixed river gage, at which it is necessary to begin
issuing warnings or river forecasts if adequate precautionary measures are to be taken
before flood stage is reached.
wash-and-strain ice foot [OCEANOGR] An ice foot formed from ice casts and slush and
attached to a shelving beach, between the high and low waterlines; high waves and
spray may cause it to build up above the high waterline.
wasp [ZOO] The common name for members of 67 families of the order Hymenoptera;
all are important as parasites or predators of injurious pests.
waste pipe [CIV ENG] Apipe to carry waste water from a basin, bath, or sink in a building.
waste plain See alluvial plain.
waste vent See stack vent.
water atmosphere [METEOROL] The concept of a separate atmosphere composed only
of water vapor.
water-bearing strata [GEOL] Ground layers below the standing water level.
water-borne [SCI TECH] Floating on or transported by water.
water budget See hydrologic accounting.
water cloud [METEOROL] Any cloud composed entirely of liquid water drops; to be
distinguished from an ice-crystal cloud and from a mixed cloud.
water conservation [ECOL] The protection, development, and efficient management
of water resources for beneficial purposes.
water content [HYD] The liquid water present within a sample of snow (or soil) usually
expressed in percent by weight; the water content in percent of water equivalent is
100 minus the quality of snow. Also known as free-water content; liquid-water content.
watercourse [HYD] 1. A stream of water. 2. A natural channel through which water
may run or does run.
water cycle See hydrologic cycle.
may run or does run.
water cycle See hydrologic cycle.
water equivalent [METEOROL] The depth of water that would result from the melting
of the snowpack or of a snow sample; thus, the water equivalent of a new snowfall
is the same as the amount of precipitation represented by that snowfall.
of the snowpack or of a snow sample; thus, the water equivalent of a new snowfall
is the same as the amount of precipitation represented by that snowfall.
water exchange [OCEANOGR] The volume and rate of water exchange between air and
a body of water in a specific location, or between several bodies of water, controlled
by such factors as tides, winds, river discharge, and currents.
a body of water in a specific location, or between several bodies of water, controlled
by such factors as tides, winds, river discharge, and currents.
waterfall [HYD] A perpendicular or nearly perpendicular descent of water in a stream.
waterfall lake See plunge pool.
waterflooding See flooding.
waterfall lake See plunge pool.
waterflooding See flooding.
water front [GEOGR] An area partly bounded by water.
water gap [GEOL] A deep and narrow pass that cuts to the base of a mountain ridge,
and through which a stream flows; the Delaware Water Gap is an example.
and through which a stream flows; the Delaware Water Gap is an example.
waterless zone [HYD] The lowest hydrologic zone, generally beginning several miles
beneath the land surface and characterized by the absence of water in the pore spaces
due to the great pressure and density of the rock.
waterline See water table.
water loss See evapotranspiration.
beneath the land surface and characterized by the absence of water in the pore spaces
due to the great pressure and density of the rock.
waterline See water table.
water loss See evapotranspiration.
water mass [OCEANOGR] A body of water identified by its temperature-salinity curve
or chemical composition, and normally consisting of a mixture of two or more water
types.
or chemical composition, and normally consisting of a mixture of two or more water
types.
water opening [OCEANOGR] A break in sea ice, revealing the sea surface.
water pollution [ECOL] Contamination of water by materials such as sewage effluent,
chemicals, detergents, and fertilizer runoff.
water requirement [HYD] The total quantity of water required to mature a specified
crop under field conditions; includes applied irrigation, water precipitation, and
groundwater available to the crop.
crop under field conditions; includes applied irrigation, water precipitation, and
groundwater available to the crop.
water retting [MICROBIO] A type of retting process in which the stalks of fiber plants
are immersed in cold or warm, slowly renewed water, for 4 days to several weeks. The
active organism is Clostridium felsineum and related types, which break down the pectin
to a mixture of organic acids (chiefly acetic and butyric), alcohols (butanol, ethanol,
and methanol), carbon dioxide (CO2), and hydrogen (H2).
are immersed in cold or warm, slowly renewed water, for 4 days to several weeks. The
active organism is Clostridium felsineum and related types, which break down the pectin
to a mixture of organic acids (chiefly acetic and butyric), alcohols (butanol, ethanol,
and methanol), carbon dioxide (CO2), and hydrogen (H2).
watershed [HYD] The drainage area of a stream.
water sky [METEOROL] The dark appearance of the underside of a cloud layer when it
is over a surface of open water.
water smoke See steam fog.
is over a surface of open water.
water smoke See steam fog.
water snow [HYD] Snow that, when melted, yields a more than average amount of
water; thus, any snow with a high water content.
waterspout [METEOROL] A tornado occurring over water; rarely, a lesser whirlwind over
water, comparable in intensity to a dust devil over land.
water; thus, any snow with a high water content.
waterspout [METEOROL] A tornado occurring over water; rarely, a lesser whirlwind over
water, comparable in intensity to a dust devil over land.
water table [HYD] The planar surface between the zone of saturation and the zone of
aeration. Also known as free-water elevation; free-water surface; groundwater level;
groundwater surface; groundwater table; level of saturation; phreatic surface; plane
of saturation; saturated surface; water level; waterline.
aeration. Also known as free-water elevation; free-water surface; groundwater level;
groundwater surface; groundwater table; level of saturation; phreatic surface; plane
of saturation; saturated surface; water level; waterline.
water type [OCEANOGR] Ocean water of a specified temperature and salinity.
water-vapor absorption [METEOROL] The absorption of certain wavelengths of infrared
radiation by atmospheric water vapor; a process of fundamental importance in the
energy budget of the earth’s atmosphere.
radiation by atmospheric water vapor; a process of fundamental importance in the
energy budget of the earth’s atmosphere.
waterwheel [ENG] A vertical wheel on a horizontal shaft that is made to revolve by the
action or weight of water on or in containers attached to the rim.
action or weight of water on or in containers attached to the rim.
water year [HYD] Any 12-month period, usually selected to begin and end during a
relatively dry season, used as a basis for processing streamflow and other hydrologic
data; the period from October 1 to September 30 is most widely used in the United
States.
relatively dry season, used as a basis for processing streamflow and other hydrologic
data; the period from October 1 to September 30 is most widely used in the United
States.
wave base [HYD] The depth at which sediments are not stirred by wave action, usually
about 33 feet (10 meters). Also known as wave depth.
wave basin [GEOGR] A basin close to the inner entrance of a harbor in which the waves
from the outer entrance are absorbed, thus reducing the size of the waves entering
the inner harbor.
about 33 feet (10 meters). Also known as wave depth.
wave basin [GEOGR] A basin close to the inner entrance of a harbor in which the waves
from the outer entrance are absorbed, thus reducing the size of the waves entering
the inner harbor.
wave cyclone [METEOROL] A cyclone which forms and moves along a front; the
circulation about the cyclone center tends to produce a wavelike deformation of the
front. Also known as wave depression.
wave depression See wave cyclone.
wave depth See wave base.
circulation about the cyclone center tends to produce a wavelike deformation of the
front. Also known as wave depression.
wave depression See wave cyclone.
wave depth See wave base.
wave disturbance [METEOROL] In synoptic meteorology, the same as wave cyclone,
but usually denoting an early state in the development of a wave cyclone, or a poorly
developed one.
wave erosion See marine abrasion.
but usually denoting an early state in the development of a wave cyclone, or a poorly
developed one.
wave erosion See marine abrasion.
wave forecasting [OCEANOGR] The theoretical determination of future wave characteristics
based on observed or forecasted meteorological phenomena.
based on observed or forecasted meteorological phenomena.
wave height [OCEANOGR] The height of a water-surface wave; generally taken as the
height difference between the wave crest and the preceding trough.
height difference between the wave crest and the preceding trough.
wave setdown [OCEANOGR] A decrease in the mean water level in the region in which
breakers form near the seashore, caused by the presence of a pressure field.
breakers form near the seashore, caused by the presence of a pressure field.
wave setup [OCEANOGR] An increase in the mean water level shoreward of the region
in which breakers form at the seashore, caused by the onshore flux of momentum
against the beach.
in which breakers form at the seashore, caused by the onshore flux of momentum
against the beach.
wave system [OCEANOGR] In ocean wave studies, a group of waves which have the
same height, length, and direction of movement.
same height, length, and direction of movement.
wave theory of cyclones [METEOROL] A theory of cyclone development based upon
the principle of wave formation on an interface between two fluids; in the atmosphere,
a front is taken as such an interface.
the principle of wave formation on an interface between two fluids; in the atmosphere,
a front is taken as such an interface.
weak acid [CHEM] An acid that does not ionize greatly; for example, acetic acid or
carbonic acid.
carbonic acid.
weather [METEOROL] 1. The state of the atmosphere, mainly with respect to its effects
upon life and human activities; as distinguished from climate, weather consists of
the short-term (minutes to months) variations of the atmosphere. 2. As used in
the making of surface weather observations, a category of individual and combined
atmospheric phenomena which must be drawn upon to describe the local atmospheric
activity at the time of observation.
upon life and human activities; as distinguished from climate, weather consists of
the short-term (minutes to months) variations of the atmosphere. 2. As used in
the making of surface weather observations, a category of individual and combined
atmospheric phenomena which must be drawn upon to describe the local atmospheric
activity at the time of observation.
weather central [METEOROL] An organization which collects, collates, evaluates, and
disseminates meteorological information in such a manner that it becomes a principal
source of such information for a given area.
disseminates meteorological information in such a manner that it becomes a principal
source of such information for a given area.
weathered iceberg [OCEANOGR] An iceberg which is irregular in shape, due to an
advanced stage of ablation; it may have overturned.
advanced stage of ablation; it may have overturned.
weather forecast [METEOROL] A forecast of the future state of the atmosphere with
specific reference to one or more associated weather elements.
specific reference to one or more associated weather elements.
weathering [GEOL] Physical disintegration and chemical decomposition of earthy and
rocky materials on exposure to atmospheric agents, producing an in-place mantle of
waste. Also known as clastation; demorphism.
rocky materials on exposure to atmospheric agents, producing an in-place mantle of
waste. Also known as clastation; demorphism.
weather map [METEOROL] A chart portraying the state of the atmospheric circulation
and weather at a particular time over a wide area; it is derived from a careful analysis
of simultaneous weather observations made at many observing points in the area.
and weather at a particular time over a wide area; it is derived from a careful analysis
of simultaneous weather observations made at many observing points in the area.
weather-map type See weather type.
weather minimum [METEOROL] The worst weather conditions under which aviation
operations may be conducted under either visual or instrument flight rules; usually
prescribed by directives and standing operating procedures in terms of minimum
ceiling, visibility, or specific hazards to flight.
operations may be conducted under either visual or instrument flight rules; usually
prescribed by directives and standing operating procedures in terms of minimum
ceiling, visibility, or specific hazards to flight.
weather modification [METEOROL] The changing of natural weather phenomena by
technical means; so far, only on the microscale of condensation and freezing nuclei
has it been possible to exert modifying influences.
technical means; so far, only on the microscale of condensation and freezing nuclei
has it been possible to exert modifying influences.
weather observation [METEOROL] An evaluation of one or more meteorological
elements that describe the state of the atmosphere either at the earth’s surface or
aloft.
elements that describe the state of the atmosphere either at the earth’s surface or
aloft.
weather shore [METEOROL] As observed from a vessel, the shore lying in the direction
from which the wind is blowing.
from which the wind is blowing.
weather side [METEOROL] The side of a ship exposed to the wind or weather.
weather signal [METEOROL] A visual signal displayed to indicate a weather forecast.
weather station [METEOROL] A place and facility for the observation, measurement,
and recording and transmission of data of the variable elements of weather; one of
the most effective network facilities is that of the U.S. Weather Bureau.
and recording and transmission of data of the variable elements of weather; one of
the most effective network facilities is that of the U.S. Weather Bureau.
weather type [METEOROL] A series of generalized synoptic situations, usually presented
in chart form; weather types are selected to represent typical pressure patterns,
and were originally devised as a method for lengthening the effective time-range of
forecasts. Also known as weather-map type.
in chart form; weather types are selected to represent typical pressure patterns,
and were originally devised as a method for lengthening the effective time-range of
forecasts. Also known as weather-map type.
Weddell Current [OCEANOGR] A surface current which flows in an easterly direction
from the Weddell Sea outside the limit of the West Wind Drift.
Wedener-Bergeron process See Bergeron-Findeisen theory.
wedge See ridge.
from the Weddell Sea outside the limit of the West Wind Drift.
Wedener-Bergeron process See Bergeron-Findeisen theory.
wedge See ridge.
weed [BOT] A plant that is useless or of low economic value, especially one growing on
cultivated land to the detriment of the crop.
weeping spring See spring seepage.
cultivated land to the detriment of the crop.
weeping spring See spring seepage.
weevil [ZOO] Any of various snout beetles whose larvae destroy crops by eating the
interior of the fruit or grain, or bore through the bark into the pith of many trees.
interior of the fruit or grain, or bore through the bark into the pith of many trees.
weighing rain gage [ENG] A type of recording rain gage, consisting of a receiver in the
shape of a funnel which empties into a bucket mounted upon a weighing mechanism;
the weight of the catch is recorded, on a clock-driven chart, as inches of precipitation;
used at climatological stations.
shape of a funnel which empties into a bucket mounted upon a weighing mechanism;
the weight of the catch is recorded, on a clock-driven chart, as inches of precipitation;
used at climatological stations.
wellhead [HYD] The place where a stream emerges from the ground.
West Australia Current [OCEANOGR] The complex current flowing northward along the
west coast of Australia; it is strongest from November to January, and weakest and
variable from May to July; it curves toward the west to join the South Equatorial
Current.
westerlies [METEOROL] The dominant west-to-east motion of the atmosphere, centered
over the middle latitudes of both hemispheres; at the earth’s surface, the westerly
belt (or west-wind belt) extends, on the average, from about 35 to 65˚latitude. Also
known as circumpolar westerlies; middle-latitude westerlies; mid-latitude westerlies;
polar westerlies; subpolar westerlies; subtropical westerlies; temperate westerlies;
zonal westerlies; zonal winds.
west coast of Australia; it is strongest from November to January, and weakest and
variable from May to July; it curves toward the west to join the South Equatorial
Current.
westerlies [METEOROL] The dominant west-to-east motion of the atmosphere, centered
over the middle latitudes of both hemispheres; at the earth’s surface, the westerly
belt (or west-wind belt) extends, on the average, from about 35 to 65˚latitude. Also
known as circumpolar westerlies; middle-latitude westerlies; mid-latitude westerlies;
polar westerlies; subpolar westerlies; subtropical westerlies; temperate westerlies;
zonal westerlies; zonal winds.
westerly wave [METEOROL] An atmospheric wave disturbance embedded in the midlatitude
westerlies.
westerlies.
Western Equatorial Countercurrent [OCEANOGR] Weak, narrow bands of eastwardflowing water observed in some winter months in the western Atlantic near the
equator.
equator.
West Greenland Current [OCEANOGR] The current flowing northward along the west
coast of Greenland into the Davis Strait; part of this current joins the Labrador Current,
while the other part continues into Baffin Bay.
coast of Greenland into the Davis Strait; part of this current joins the Labrador Current,
while the other part continues into Baffin Bay.
westward intensification [OCEANOGR] The intensification of ocean currents to the
west, derived from a mathematical model that includes the effects of zonal wind
stress at the sea surface and internal friction.
West Wind Drift See Antarctic Circumpolar Current.
west, derived from a mathematical model that includes the effects of zonal wind
stress at the sea surface and internal friction.
West Wind Drift See Antarctic Circumpolar Current.
wet-bulb depression [METEOROL] The difference in degrees between the dry-bulb
temperature and the wet-bulb temperature.
temperature and the wet-bulb temperature.
wet-bulb temperature [METEOROL] 1. Isobaric wet-bulb temperature, that is, the
temperature an air parcel would have if cooled adiabatically to saturation at constant
pressure by evaporation of water into it, all latent heat being supplied by the parcel.
2. The temperature read from the wet-bulb thermometer; for practical purposes, the
temperature so obtained is identified with the isobaric wet-bulb temperature.
temperature an air parcel would have if cooled adiabatically to saturation at constant
pressure by evaporation of water into it, all latent heat being supplied by the parcel.
2. The temperature read from the wet-bulb thermometer; for practical purposes, the
temperature so obtained is identified with the isobaric wet-bulb temperature.
wet climate [CLIMATOL] Aclimate whose vegetation is of the rainforest type. Also known
as rainforest climate.
as rainforest climate.
wet gas [PETR MIN] Natural gas produced along with crude petroleum in oil fields or
from gas-condensate fields; in addition to methane, it contains ethane, propane,
from gas-condensate fields; in addition to methane, it contains ethane, propane,
butanes, and some higher hydrocarbons, such as pentane and hexane.
wetlands [ECOL] An area characterized by a high content of soil moisture, such as a
swamp or bog.
wet season See rainy season.
swamp or bog.
wet season See rainy season.
wet snow [METEOROL] Deposited snow that contains a great deal of liquid water.
wheat [BOT] A food grain crop of the genus Triticum; plants are self-pollinating; the
inflorescence is a spike bearing sessile spikelets arranged alternately on a zigzag
rachis.
whippoorwill storm See frog storm.
inflorescence is a spike bearing sessile spikelets arranged alternately on a zigzag
rachis.
whippoorwill storm See frog storm.
whirlpool [OCEANOGR] Water in rapid rotary motion.
whirly [METEOROL] A small violent storm, a few yards (or meters) to 100 yards
(91 meters) or more in diameter, frequent in Antarctica near the time of the equinoxes.
white ant See termite.
(91 meters) or more in diameter, frequent in Antarctica near the time of the equinoxes.
white ant See termite.
white band disease [ZOO] A coral reef disease that is typified by a loss of tissue that
is visible as a band of bare white skeleton.
whitecap [OCEANOGR] A cloud of bubbles at the sea surface caused by a breaking wave.
white copperas See zinc sulfate.
is visible as a band of bare white skeleton.
whitecap [OCEANOGR] A cloud of bubbles at the sea surface caused by a breaking wave.
white copperas See zinc sulfate.
white damp [PETR MIN] In mining, carbon monoxide (CO); a gas that may be present
in the afterdamp of a gas or coal-dust explosion, or in the gases given off by a mine
fire; it is an important constituent of illuminating gas, supports combustion, and is
very poisonous.
in the afterdamp of a gas or coal-dust explosion, or in the gases given off by a mine
fire; it is an important constituent of illuminating gas, supports combustion, and is
very poisonous.
white diarrhea See pullorum disease.
white frost See hoarfrost.
white frost See hoarfrost.
white lead [CHEM] Basic lead carbonate of variable composition, the oldest and most
important lead paint pigment; also used in putty and ceramics.
important lead paint pigment; also used in putty and ceramics.
white light [PHYS] Any radiation producing the same color sensation as average noon
sunlight.
sunlight.
whiteout [METEOROL] An atmospheric optical phenomenon of the polar regions in
which the observer appears to be engulfed in a uniformly white glow:shadows, horizon,
and clouds are not discernible; sense of depth and orientation are lost; dark objects
in the field of view appear to float at an indeterminable distance. Also known as milky
weather.
which the observer appears to be engulfed in a uniformly white glow:shadows, horizon,
and clouds are not discernible; sense of depth and orientation are lost; dark objects
in the field of view appear to float at an indeterminable distance. Also known as milky
weather.
white phosphorus [CHEM] The element phosphorus in its allotropic form, a soft, waxy,
poisonous solid melting at 44.5˚C; soluble in carbon disulfide, insoluble in water and
alcohol; self-igniting in air. Also known as yellow phosphorus.
poisonous solid melting at 44.5˚C; soluble in carbon disulfide, insoluble in water and
alcohol; self-igniting in air. Also known as yellow phosphorus.
white squall [METEOROL] A sudden squall in tropical or subtropical waters, which lacks
the usual squall cloud and whose approach is signaled only by the whiteness of a line
of broken water or whitecaps.
white vitriol See zinc sulfate.
the usual squall cloud and whose approach is signaled only by the whiteness of a line
of broken water or whitecaps.
white vitriol See zinc sulfate.
white water [OCEANOGR] Frothy water, as in whitecaps or breakers.
whiting [OCEANOGR] A patch of seawater that contains a substantial amount of calcium
carbonate and therefore appears white relative to surrounding water.
carbonate and therefore appears white relative to surrounding water.
whole-body counter [ENG] A radiation counter that directly measures radioactivity in
the entire human body.
the entire human body.
whole gale [METEOROL] 1. In storm-warning terminology, a wind of 48 to 63 knots (55
to 72 miles, or 89 to 133 kilometers, per hour). 2. In the Beaufort wind scale, a wind
whose speed is from 48 to 55 knots (55 to 63 miles, or 89 to 102 kilometers, per hour).
to 72 miles, or 89 to 133 kilometers, per hour). 2. In the Beaufort wind scale, a wind
whose speed is from 48 to 55 knots (55 to 63 miles, or 89 to 102 kilometers, per hour).
whooping cough See pertussis.
whorl [BOT] An arrangement of several identical anatomical parts, such as petals, in a
circle around the same point.
Wiesen See meadow.
circle around the same point.
Wiesen See meadow.
Wild fence [METEOROL] A wooden enclosure about 16 feet 4.8 meters square and 8 feet
2.4 meters high with a precipitation gage in its center; the function of the fence is to
minimize eddies around the gage, and thus ensure a catch which will be representative
of the actual rainfall or snowfall.
2.4 meters high with a precipitation gage in its center; the function of the fence is to
minimize eddies around the gage, and thus ensure a catch which will be representative
of the actual rainfall or snowfall.
wildfire [FOR] An uncontrolled fire that burns surface vegetation (grass, weeds,
grainfields, brush, chaparral, tundra, and forest and woodland). [PL PATH] A
bacterial disease of tobacco caused by Pseudomonas tabaci and characterized by the
appearance of brown spots surrounded by yellow rings, which turn dark, rot, and fall
out.
wild snow [METEOROL] Newly deposited snow which is very fluffy and unstable; in
general, it falls only during a dead calm at very low air temperatures.
grainfields, brush, chaparral, tundra, and forest and woodland). [PL PATH] A
bacterial disease of tobacco caused by Pseudomonas tabaci and characterized by the
appearance of brown spots surrounded by yellow rings, which turn dark, rot, and fall
out.
wild snow [METEOROL] Newly deposited snow which is very fluffy and unstable; in
general, it falls only during a dead calm at very low air temperatures.
wilt [PL PATH] Any of various plant diseases characterized by drooping and shriveling,
following loss of turgidity.
following loss of turgidity.
wilting point [BOT] A condition in which a plant begins to use water from its own tissues
for transpiration because soil water has been exhausted.
for transpiration because soil water has been exhausted.
wind [METEOROL] The motion of air relative to the earth’s surface; usually means
horizontal air motion, as distinguished from vertical motion, and air motion averaged
over the response period of the particular anemometer.
horizontal air motion, as distinguished from vertical motion, and air motion averaged
over the response period of the particular anemometer.
windburn [BOT] Injury to plant foliage, caused by strong, hot, dry winds.
wind chill [METEOROL] That part of the total cooling of a body caused by air motion.
wind-chill index [METEOROL] The cooling effect of any combination of temperature
and wind, expressed as the loss of body heat in kilogram calories per hour per square
meter of skin surface; it is only an approximation because of individual body variations
in shape, size, and metabolic rate.
and wind, expressed as the loss of body heat in kilogram calories per hour per square
meter of skin surface; it is only an approximation because of individual body variations
in shape, size, and metabolic rate.
wind crust [HYD] A type of snow crust, formed by the packing action of wind on
previously deposited snow; wind crust may break locally but, unlike wind slab, does
not constitute an avalanche hazard.
previously deposited snow; wind crust may break locally but, unlike wind slab, does
not constitute an avalanche hazard.
wind current [METEOROL] Generally, any of the quasi-permanent, large-scale wind
systems of the atmosphere, for example, the westerlies, trade winds, equatorial
easterlies, or polar easterlies.
systems of the atmosphere, for example, the westerlies, trade winds, equatorial
easterlies, or polar easterlies.
wind direction [METEOROL] The direction from which wind blows.
wind divide [METEOROL] A semipermanent feature of the atmospheric circulation
(usually a high-pressure ridge) on opposite sides of which the prevailing wind
directions differ greatly.
(usually a high-pressure ridge) on opposite sides of which the prevailing wind
directions differ greatly.
wind drift See drift current.
wind-driven current See drift current.
wind erosion [GEOL] Detachment, transportation, and deposition of loose topsoil or
sand by the action of wind.
sand by the action of wind.
wind measurement [METEOROL] The determination of three parameters:the size of an
air sample, its speed, and its direction of motion.
air sample, its speed, and its direction of motion.
window [HYD] The unfrozen part of a river surrounded by river ice during the winter.
window frost [HYD] A thin deposit of hoarfrost often found on interior surfaces of
windows in winter, and frequently exhibiting beautiful fernlike patterns.
windows in winter, and frequently exhibiting beautiful fernlike patterns.
window ice [HYD] A thin deposit of ice which forms by the freezing of many tiny drops
of water that have condensed on the indoors side of a cold window surface.
of water that have condensed on the indoors side of a cold window surface.
wind power [ENG] The extraction of kinetic energy from the wind and conversion of it
into a useful type of energy:thermal, mechanical, or electrical.
into a useful type of energy:thermal, mechanical, or electrical.
wind ripple [METEOROL] One of a series of wavelike formations on a snow surface, an
inch or so in height, at right angles to the direction of wind. Also known as snow ripple.
inch or so in height, at right angles to the direction of wind. Also known as snow ripple.
wind rose [METEOROL] A diagram in which statistical information concerning direction
and speed of the wind at a locationmaybe summarized; a line segment is drawn in each
of perhaps eight compass directions from a common origin; the length of a particular
segment is proportional to the frequency with which winds blow from that direction;
thicknesses of a segment indicate frequencies of occurrence of various classes of wind
speed.
and speed of the wind at a locationmaybe summarized; a line segment is drawn in each
of perhaps eight compass directions from a common origin; the length of a particular
segment is proportional to the frequency with which winds blow from that direction;
thicknesses of a segment indicate frequencies of occurrence of various classes of wind
speed.
windrow [GEOL] Any accumulation of material formed by wind or tide action.
winds aloft [METEOROL] Generally, the wind speeds and directions at various levels in
the atmosphere above the domain of surface weather observations, as determined
by any method of winds-aloft observation. Also known as upper-level winds; upper
winds.
winds-aloft observation [METEOROL] The measurement and computation of wind
speeds and directions at various levels above the surface of the earth.
wind scoop [METEOROL] A saucerlike depression in the snow near obstructions such
as trees, houses, and rocks, caused by the eddying action of the deflected wind.
wind shear [METEOROL] The local variation of the wind vector or any of its components
in a given direction.
wind-shift line [METEOROL] A line or narrow zone along which there is an abrupt change
of wind direction.
wind slab [HYD] A type of snow crust; a patch of hard-packed snow, which is packed as
it is deposited in favored spots by the wind, in contrast to wind crust.
wind speed [METEOROL] The rate of motion of air.
windstorm [METEOROL] A storm in which strong wind is the most prominent
characteristic.
wind stress [METEOROL] The drag or tangential force per unit area exerted on the
surface of the earth by the adjacent layer of moving air.
wind tide [OCEANOGR] 1. The vertical rise in the still-water level on the leeward side of
a body of water, particularly the ocean or other large body, caused by wind stresses on
the surface of the water. 2. The difference in still-water level between the windward
and leeward sides of such a body caused by wind stresses.
wind turbine [ENG] Machine that converts wind power to electricity; as moving air
flows past the rotors of the turbine, the rotors spin and drive the shaft of an electric
generator.
wind velocity [METEOROL] The speed and direction of wind.
windward [METEOROL] In the general direction from which the wind blows.
wind wave [OCEANOGR] A wave resulting from the action of wind on a water surface.
wing See vesicle.
winged headland [GEOGR] A seacliff with two bays or spits, one on either side.
winter ice [OCEANOGR] Level sea ice more than 8 inches (20 centimeters) thick, and
less than 1 year old; the stage which follows young ice.
Witte-Margules equation [OCEANOGR] A formula expressing the slope of the boundary
layer between two water masses of different densities and velocities, taking into
account the rotation of the earth. Also known as Margules equation.
wood [ECOL] A dense growth of trees, more extensive than a grove and smaller than a
forest.
woodland See forest; temperate woodland.
wood preservative [ENG] A material used to coat wood to kill insects and fungi, but
not usually classed as an insecticide; coal tar creosote and its derivatives are the most
widely used wood preservatives.
wood pulp See pulp.
woodstone See silicified wood.
wool-sorter’s disease See anthrax.
worker [ZOO] One of the neuter, usually sterile individuals making up a caste of social
insects, such as ants, termites, or bees, which labor for the colony.
the atmosphere above the domain of surface weather observations, as determined
by any method of winds-aloft observation. Also known as upper-level winds; upper
winds.
winds-aloft observation [METEOROL] The measurement and computation of wind
speeds and directions at various levels above the surface of the earth.
wind scoop [METEOROL] A saucerlike depression in the snow near obstructions such
as trees, houses, and rocks, caused by the eddying action of the deflected wind.
wind shear [METEOROL] The local variation of the wind vector or any of its components
in a given direction.
wind-shift line [METEOROL] A line or narrow zone along which there is an abrupt change
of wind direction.
wind slab [HYD] A type of snow crust; a patch of hard-packed snow, which is packed as
it is deposited in favored spots by the wind, in contrast to wind crust.
wind speed [METEOROL] The rate of motion of air.
windstorm [METEOROL] A storm in which strong wind is the most prominent
characteristic.
wind stress [METEOROL] The drag or tangential force per unit area exerted on the
surface of the earth by the adjacent layer of moving air.
wind tide [OCEANOGR] 1. The vertical rise in the still-water level on the leeward side of
a body of water, particularly the ocean or other large body, caused by wind stresses on
the surface of the water. 2. The difference in still-water level between the windward
and leeward sides of such a body caused by wind stresses.
wind turbine [ENG] Machine that converts wind power to electricity; as moving air
flows past the rotors of the turbine, the rotors spin and drive the shaft of an electric
generator.
wind velocity [METEOROL] The speed and direction of wind.
windward [METEOROL] In the general direction from which the wind blows.
wind wave [OCEANOGR] A wave resulting from the action of wind on a water surface.
wing See vesicle.
winged headland [GEOGR] A seacliff with two bays or spits, one on either side.
winter ice [OCEANOGR] Level sea ice more than 8 inches (20 centimeters) thick, and
less than 1 year old; the stage which follows young ice.
Witte-Margules equation [OCEANOGR] A formula expressing the slope of the boundary
layer between two water masses of different densities and velocities, taking into
account the rotation of the earth. Also known as Margules equation.
wood [ECOL] A dense growth of trees, more extensive than a grove and smaller than a
forest.
woodland See forest; temperate woodland.
wood preservative [ENG] A material used to coat wood to kill insects and fungi, but
not usually classed as an insecticide; coal tar creosote and its derivatives are the most
widely used wood preservatives.
wood pulp See pulp.
woodstone See silicified wood.
wool-sorter’s disease See anthrax.
worker [ZOO] One of the neuter, usually sterile individuals making up a caste of social
insects, such as ants, termites, or bees, which labor for the colony.
X
xanthan gum [BIOL] A polysaccharide produced by the bacterium Xanthomonas campestris that is used as a thickener and stabilizer in foods; also used in oil recovery to help improve water flooding and oil displacement.
xanthene [CHEM] CH2 (C6H4)2O Yellowish crystals that are soluble in ether, slightly soluble in water and alcohol; melts at 100˚C; used as a fungicide and chemical intermediate. Also known as tricyclic dibenzopyran.
9-xanthenone See genicide.
Xanthomonas citri [MICROBIO] The bacterial pathogen that causes citrus canker.
xanthone [CHEM] CO(C6H4)2O White needle crystals that are found in some plant pigments; insoluble in water, soluble in alcohol, chloroform, and benzene; melts at 173˚C, sublimes at 350˚C; used as a larvicide, as a dye intermediate, and in perfumes and pharmaceuticals.
xenogamy [BOT] Cross-fertilization between flowers on different plants.
xenon [CHEM] An element, symbol Xe, member of the noble gas family, group 0, atomic number 54, atomic weight 131.291; colorless, boiling point −108˚C (1 atmosphere, or 101,325 pascals), noncombustible, nontoxic, and nonreactive; used in photographic flash lamps, luminescent tubes, and lasers, and as an anesthetic.
xerarch succession [ECOL] A type of succession that originates in a dry habitat
xeric [ECOL] 1. Of or pertaining to a habitat having a low or inadequate supply of moisture. 2. Of or pertaining to an organism living in such an environment
xeromorphic [ECOL] Referring to a plant that is able to survive in dry environments.
xerophyte [ECOL] A plant adapted to life in areas where the water supply is limited.
xerosere [ECOL] A temporary community in an ecological succession on dry, sterile ground such as rock, sand, or clay.
xerothermic [CLIMATOL] Characterized by dryness and heat.
xerotolerance [BIOL] The ability to grow in extremely dry habitats.
xylem [BOT] The principal water-conducting tissue and the chief supporting tissue of higher plants; composed of tracheids, vessel members, fibers, and parenchyma.
xylene [CHEM] C6H4(CH3)2 Any one of the family of isomeric, colorless aromatic hydrocarbon liquids, produced by the destructive distillation of coal or by the catalytic reforming of petroleum naphthenic fractions; used for high-octane and aviation gasolines, solvents, chemical intermediates, and the manufacture of polyester resins. Also known as dimethylbenzene; xylol.
ortho-xylene [CHEM] 1,2-C6H4(CH3)2 A flammable, moderately toxic liquid; insoluble in water, soluble in alcohol and ether; boils at 144˚C; used to make phthalic anhydride, vitamins, pharmaceuticals, and dyes, and in insecticides and motor fuels.
xylenol [CHEM] (CH3)2C6H3OH Highly toxic, combustible crystals; slightly soluble in water, soluble in most organic solvents; melts at 20–76˚C; used as a chemical intermediate, disinfectant, solvent, and fungicide, and for pharmaceuticals and dyestuffs.
xylol See xylene.
xylophagous [BIOL] Referring to an organism which feeds on wood.
Y
yaws [MED] An infectious tropical disease of humans caused by the spirochete
Treponema pertenue; manifested by a primary cutaneous lesion followed by a
granulomatous skin eruption.
yeast [MYCOL] A collective name for those fungi which possess, under normal
conditions of growth, a vegetative body (thallus) consisting, at least in part, of simple, individual cells.
yellow dwarf [PL PATH] Any of several plant viral diseases characterized by yellowing of the foliage and stunting of the plant.
yellow-green algae [BOT] The common name for members of the class Xanthophyceae.
yellow phosphorus See white phosphorus.
yellows [PL PATH] Any of various fungus diseases of plants characterized by yellowing of the leaves which later turn brown, become brittle, and die; affects cabbage, lettuce, cauliflower, peach, sugarbeet, and other plants.
Yellow Sea [GEOGR] An inlet of the Pacific Ocean between northeastern China and Korea.
yellow snow [HYD] Snow with a golden or yellow appearance because of the presence of pine or cypress pollen.
young ice [HYD] Newly formed ice in the transitional stage of development from ice crust to winter ice.
Yucat´an Current [OCEANOGR] A rapid northward flowing current along the western side of the Yucatｴan Strait; generally loops to the north and exits as the Florida Current.
Z
zastruga See sastruga.
Zeitgeber [BIOL] A periodic environmental condition or event that acts to set or reset an innate biological rhythm of an organism.
zenithal rain [METEOROL] In the tropics or subtropics, the rainy season which recurs annually or semiannually at about the time that the sun is most nearly overhead (at zenith).
zephyr [METEOROL] Any soft, gentle breeze.
zero layer [OCEANOGR] A reference level in the ocean, at which horizontal motion is at a minimum.
zero population growth [ECOL] Situation in which each organism in a population is replaced by only one offspring, so there is no increase in population size.
zinc arsenite [CHEM] Zn(AsO2)2 A toxic white powder that is insoluble in water, soluble in alkalies; used as an insecticide and timber preservative. Also known as zinc metaarsenite.
zinc chloride [CHEM] ZnCl2 Water- and alcohol-soluble, white, fire-hazardous crystals that melt at 290˚C, and are irritating to the skin; used as a catalyst and in electroplating, wood preservation, textile processing, petroleum refining, medicine, and feed additives.
zinc metaarsenite See zinc arsenite.
zinc naphthenate [CHEM] Zn(C6H5COO)2 A combustible, viscous, acetone-soluble solid; used in paints, varnishes, and resins, and as a drier and wetting agent, insecticide, fungicide, and mildewstat.
zinc orthoarsenate [CHEM] Zn3 (AsO4)2 A toxic white powder that is insoluble in water, soluble in alkalies; used as an insecticide and wood preservative.
zinc sulfate [CHEM] ZnSO4ｷ7H2O Efflorescent, water-soluble, colorless crystals with an astringent taste; used to preserve skins and wood and as a paper bleach, analytical reagent, feed additive, and fungicide. Also known as white copperas; white vitriol; zinc vitriol.
zinc sulfide [CHEM] ZnS A yellowish powder that is insoluble in water, soluble in acids; exists in two crystalline forms (alpha, or wurtzite, and beta, or sphalerite); beta becomes alpha at 1020˚C, and sublimes at 1180˚C; used as a pigment for paints and linoleum, in opaque glass, rubber, and plastics, for hydrosulfite dyeing process, as x-ray and television screen phosphor, and as a fungicide.
zinc vitriol See zinc sulfate.
zonal [METEOROL] Latitudinal, easterly or westerly, opposed to meridional.
zonal circulation See zonal flow.
zonal flow [METEOROL] The flow of air along a latitude circle; more specifically, the latitudinal (east or west) component of existing flow. Also known as zonal circulation.
zonal index [METEOROL] A measure of strength of the middle-latitude westerlies, expressed as the horizontal pressure difference between 35˚and 55˚latitude, or as the corresponding geostrophic wind.
zonal kinetic energy [METEOROL] The kinetic energy of the mean zonal wind, obtained by averaging the zonal component of the wind along a fixed latitude circle.
zonal soil [GEOL] In early classification systems in the United States, a soil order including soils with well-developed characteristics that reflect the influence of agents of soil genesis. Also known as mature soil.
zonal westerlies See westerlies.
zonal wind [METEOROL] The wind, or wind component, along the local parallel of latitude, as distinguished from the meridional wind.
zonal winds See westerlies.
zonal wind-speed profile [METEOROL] A diagram in which the speed of the zonal flow is one coordinate and latitude the other.
zonation [ECOL] Arrangement of organisms in biogeographic zones.
zone [GEOGR] An area or region of latitudinal character. [GEOL] A belt, layer, band, or strip of earth material such as rock or soil.
zone of accumulation See B horizon.
zone of aeration [GEOL] The subsurface sediment above the water table containing air and water. Also known as unsaturated zone; vadose zone; zone of suspended water.
zone of illuviation See B horizon.
zone of maximum precipitation [METEOROL] In a mountain region, the belt of elevation at which the annual precipitation is greatest.
zone of saturation [HYD] A subsurface zone in which water fills the interstices in soil and is under pressure greater than atmospheric pressure; the top of the zone of saturation marks the water table for the area. Also known as phreatic zone; saturated zone.
zone of soil water See belt of soil water.
zone of suspended water See zone of aeration.
zoocecidium [PL PATH] A plant gall usually caused by an insect.
zoochlorellae [BIOL] Unicellular green algae which live as symbionts in the cytoplasm of certain protozoans, sponges, and other invertebrates.
zoochory [BOT] Dispersal of plant disseminules by animals.
zoogeographic region [ECOL] A major unit of the earth’s surface characterized by faunal homogeneity.
zoogeography [BIOL] The science that attempts to describe and explain the distribution of animals in space and time.
zoology [BIOL] The science that deals with knowledge of animal life.
zoonoses [BIOL] Diseases which are biologically adapted to and normally found in lower animals but which under some conditions also infect humans.
zooplankton [ECOL] Microscopic animals which move passively in aquatic ecosystems.
zoosphere [ECOL] The world community of animals.
zoosporangium [BOT] A spore case bearing zoospores.
zootoxin [BIOL] A toxic substance or poison produced by an animal, for example, snake venom.
zooxanthellae [BIOL] Microscopic yellow-green algae which live symbiotically in certain radiolarians and marine invertebrates.
zoster See herpes zoster.
zygospore [BOT] A thick-walled cell or resting spore that results from the fusion of similar reproductive cells, especially in organisms that reproduce by conjugation.
zymosis See fermentation.
Zythiaceae [MYCOL] A family of fungi of the order Sphaeropsidales which contains many plant and insect pathogens.
Labels: Dictionary
Subscribe to Posts [Atom]
