Remote Sensing Glossary

Reference Information for Virtual Nebraska

Terms, Definitions and Concepts

W

W

Degrees west longitude, referenced to the Greenwich (prime) meridian.

water vapor (aka moisture)

Water in a gaseous form.

wave

1. In electricity, a periodic variation of an electric current or voltage.
2. In physics, any of the series of advancing impulses set up by a vibration, pulsation, or disturbance in air or some other medium, as in the transmission of heat, light, sound, etc.

wavelength

Physical distance of one period (wave repeat).

weather

Atmospheric condition at any given time or place. Compare with climate.

Weather Facsimile (WEFAX)

A system for transmitting visual reproductions of weather forecast maps, temperature summaries, cloud analyses, etc. via radio waves. WEFAX transmissions are relayed by NOAA's geostationary GOES spacecraft.

weather symbols

Some commonly used symbols are: weather terms:

Clear

Sky cloud-free to 30 percent covered.

Sunny

Sunshine 70-100 percent of the day.

Partly sunny and partly cloudy

Both terms refer to 30 to 70 percent cloud cover. Partly sunny is used in the day; partly cloudy is used at night.

Fog

A cloud on the ground. Fog is composed of billions of tiny water droplets floating in the air.

Snow

Precipitation of ice crystals.

Snow flurries

Intermittent snowfall that may result in little accumulation.

Sleet

Pellets of ice that form when rain or melting snowflakes freeze while falling. (Occurs in cold weather; hail usually occurs in summer.)

Freezing rain

Rain that turns to ice on impact with the surface.

Rain

Extended period of precipitation. Associated with large storm systems rather than single clouds or thunder storms.

Showers

Brief interval of rain that does not affect a large area.

Squall

Fast-moving thunderstorm or line of thunderstorms that often can produce damaging winds, hail, and tornadoes.

Hail

Pieces of ice that fall from thunderstorms. Hail often is composed of concentric rings of ice that form as the particle moves through "wet" and "dry" areas of the thunderstorm.

Weather watch

Statement about a particularly dangerous weather system that may occur at some specified time in the future.

Weather warning

Statement that dangerous weather is likely or is occurring. Take action.

WEFAX

See weather facsimile.

willy-willy

Australian term for tropical cyclone, hurricane.

wind

A natural motion of the air, especially a noticeable current of air moving in the atmosphere parallel to the Earth's surface. Winds are caused by unequal heating and cooling of the Earth and atmosphere due to absorbed, incoming solar radiation and infrared radiation lost to space--as modified by such effects as the Coriolis force, the condensation of water vapor, the formation of clouds, the interaction of air masses and frontal systems, friction over land and water, etc.

The preceding chart is an abbreviated version of the Beaufort Wind Scale, named for the British admiral who invented it in 1805.

wind chill

The wind can reduce significantly the amount of heat your body retains. The following wind chill chart does not take into account such variables as type of clothing worn, amount of exposed flesh, and physical condition, all of which would alter body heat.

wind vane

An instrument used to indicate wind direction.

wind vector

Arrow representing wind velocity. The arrow points in the direction of the wind. The length of the arrow is proportional to wind speed.

wind velocity

Vector term that includes both wind speed and wind direction.

window

Term used to denote a region of the electromagnetic spectrum where the atmosphere does not absorb radiation strongly.

WOCE

See World Ocean Circulation Experiment.

workstation

A "smart" computer terminal that serves as a primary scientific research tool, offering direct access to experimental apparatus, information files, internal computers, and output devices, usually connected to an external communications network.

World Ocean Circulation Experiment (WOCE)

A study of the general global circulation of the oceans. It emphasizes the measurements and understanding needed to describe and understand the circulation, to simulate it, and to predict its changes in response to climatic changes.

WWW

World Weather Watch.

Z

zephyr

A Mediterranean term for any soft, gentle breeze.