A conductor or system of conductors for radiating and/or receiving radio energy. Also called aerial.

An instrument for measuring the ultraviolet in solar and sky radiation.

Transmitted energy which is modulated in order to carry information. Usually, it is in the form of a radio- frequency sine wave, modulated either in amplitude or in frequency.

The water portion of the earth as distinguished from the solid part, called the lithosphere, and from the gaseous outer envelope, called the atmosphere.

The scientific study of the waters of the earth, especially with relation to the effects of precipitation and evaporation upon the occurrence and character of water in streams, lakes, and on or below the land surface. In terms of the hydrologic cycle, the ...

A local variation in the wind direction or speed. This condition can present danger to aircraft, especially at landing, when a sudden shift from headwind to tailwind can cause a rapid loss of airspeed and lift.

A synoptic code approved by the World Meteorological Organization in which the observable meteorological elements are encoded and transmitted in "words" of five numerical digits length. Often abbreviated synoptic code.

The amount of moisture which, if available, would be removed from a given land area by evapotranspiration. Expressed in units of water depth.

A rain gauge capable of measuring very small amounts of precipitation. Also called micropluviometer, trace recorder.

The greatest distance at which it is just possible to see and recognize with the unaided eye (1) in the daytime, a prominent dark object against the sky at the horizon, and (2) at night, a known, preferably unfocused, moderately intense light source.

The total area drained by a river and its tributaries. Same as watershed.

A device that combines several separate communications signals into one and outputs them on a single line.

Same as instrument shelter.

film hygrometer element-An electrical hygrometer element constructed of a plastic strip coated with a film of carbon black dispersed in a hygroscopic binder. Variations in atmospheric moisture content vary the volume of the binder and thus change the resi ...

A device for measuring sea-surface waves. It consists of a weighted pole below which a disk is suspended at a depth sufficiently deep for the wave motion associated with deepwater waves to be negligible. The pole will then remain nearly as if anchored to ...

An instrument that shows changes in humidity.

In Jeffreys' classification, a wind for which the pressure force exactly balances the viscous force, in which the vertical transfers of momentum predominate.

A unit of pressure which directly expresses the force exerted by the atmosphere. Equal to 1000 dynes/cm2 or 100 pascals.

A set of weekly colored rainbow arcs sometimes discernable inside a primary rainbow.

A rotation anemometer which has a horizontal axis upon which helicoidal shaped vanes are mounted. See windmill anemometer.