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 ...

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

See calorie.

Situated on the side from which the wind blows.

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

A very sensitive electrostatic electrometer for measuring small potential differences.

See feed.

The decrease of an atmospheric variable with height, the variable being temperature, unless otherwise specified.

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.

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 ...

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

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.

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

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 ...

Same as windsock.

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

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

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.