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 instrument designed to study small fluctuations of some quantity. The microbarograph is an example of a recording pressure variometer.

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

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

See feed.

Part of a computer word that has meaning in itself, often, a byte.

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

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

Situated on the side from which the wind blows.

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.

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

The height of the cloud base above the local terrain.

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

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.

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 ...

See radiosonde commutator.

A type of precipitation composed of unbranched crystals in the form of needles, columns, or plates. Usually has a very slight downward motion and may fall from a cloudless sky.

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

An absolute pyhrliometer, developed by C.G. Abbott, in which the radiation-sensing element is a blackened water-calorimeter.