A decrease in the central pressure of a pressure system. Usually applied to a low rather than to a high.

Air in motion relative to the surface of the earth. Almost exclusively used to denote the horizontal component.

A type of cloud height indicator which uses a searchlight to project vertically a narrow beam of light onto the cloud base. The height of the cloud is determined using a clinometer, located at a known distance from the ceiling light, to measure the angle ...

A thermometer consisting of a clock mechanism the speed of which is a function of temperature.

Video Display Terminal. An input and display device which includes a keyboard and a screen and allows a human to communicate with a computer.

A clock-driven instrument mounting which automatically and continuously points in the direction of the sun. It is used with a pyrheliometera,hen continuous direct solar radiation measurements are required.

General name for an instrument which measures the earth's magnetic field intensity.

A radiosonde which transmits the indication of the meteorological sensing elements in the form of a code consisting of combinations of dots and dashes.

The atmospheric pressure at mean sea level either directly measured by stations at sea level or empirically determined from the station pressure and temperature by stations not at sea level. Used as a common reference for analyses of surface pressure patt ...

A rain gauge or array of rain gauges designed to measure the inclination and direction of falling rain.

A very sensitive electrostatic electrometer for measuring small potential differences.

See feed.

The height of the cloud base above the local terrain.

A large body of air having similar horizontal temperature and moisture characteristics.

See radiosonde commutator.

Same as windsock.

An instrument for measuring the pressure of gases and vapors. A mercury barometer is a type of manometer.

In physics, any process in which the flux density (or power, amplitude, intensity, illuminance, etc.) of a "parallel beam" of energy decreases with increasing distance from the source. Attenuation is always due to the action of the transmitting medium its ...

Abbreviation for Instrument Flight Rules, but commonly used to refer to the weather and/or flight conditions to which these rules apply, i.e. low visibility.

Generally, an instrument designed to measure or estimate the blueness of the sky. See Linke-scale.