An instrument for measuring the pressure of the atmosphere. The two principle types are aneroid and mercurial.

A fixed-length group of bits representing the large data element handled as a unit by a computer. Word length is determined by the capacity of the CPU registers.

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.

A basic equation in night visual range theory, relating the illuminance of a point source of light to distance and the transmissivity of the atmosphere.

The group of bits which a computer processes as a unit; often, 8 bits.

Same as luminous intensity.

A unit of pressure equal to 10' dyne per cm-' (101 barye), 1000 millibars. 29.53 inches of mercury.

Area of a computer or other device where various logic and control elements are interconnected. Often a printed circuit board into which other circuit boards plug at right angles.

An instrument which indicates the presence of dust particles in the atmosphere. Also spelled coniscope.

A forecast of weather elements of particular interest to aviation; including ceiling, visibility, upper winds, icing, turbulence, precipitation types, and storms.

The range through which the input may be varied without initiating a response. Usually expressed as a percentage of full-scale range.

A hygrometer in which the sensitive element is a strand or strands of human hair, the length of which is a function of the relative humidity of the air.

A medium-sized instrument shelter. It is a white louvered box with a flat double to of and is mounted four feet above the ground on a four-legged stand.

A method of streamflow routing which assumes that storage is a linear function of the weighted flow in the reach and is adaptable to a simple mathematical solution.

A river gauge in which a weight suspended on a wire is lowered to the water surface from a bridge or other overhead structure to measure the distance from a point of known elevation to the water surface.

A special form of the aspiration psychrometer. developed by Assmann, in which the thermometric elements are well shielded from radiation. Psychrometric measurements may be taken with the instrument in the presence of direct solar radiation.

Same as atmospheric pressure.

An instrument for determining the dust content of a sample of air. Also spelled conimeter.

See river basin.

See instrument error, observational error. random error, standard error, systematic error.