A polarimeter utilizing a Wollaston prism as a polarizer and a Nicol prism as an analyzer.

A type of instrument shelter. It is a wooden box painted white with double louvered sides and mounted on a stand four feet above the ground.

An absolute temperature scale with the ice point of pure water defined as 273.16 K. The size of the degree is the same as on the Celsius scale, and the zero point is absolute zero.

A halo consisting of a faint white circle passing through the Sun and running parallel to the horizon for as much as 360

Name sometimes given to a transmissometer.

The total infrared radiation emitted from the earth's surface. To be carefully distinguished from atmospheric radiation, effective terrestrial radiation, and insolation.

Radiation coming from the solid angle of the sun's disc, as opposed to diffuse sky radiation, effective terrestrial radiation, or radiation from any other source. Direct solar radiation is measured by pyrheliometers.

Erasable Programmable Read Only Memory. Programable read-only memory which can be erased, usually by ultraviolet light, and re-programmed.

The ratio of the actual amount of water evaporated into the atmosphere to the evaporative power. Also called relative evaporation.

The gravity flow of water within soil.

An instrument which measures the instantaneous rate at which rain is falling on a given surface. Also called a rate-of-rainfall gauge.

A measure, proposed by Angstrom, of the precipitation effectiveness of a region.

Sir Napier Shaw's name for the approximate absolute temperature scale,

A hygrometer using goldbeater's skin as the sensitive element. Variations of the physical dimensions of the skin caused by its hygroscopic character indicate relative humidity. (Note: Goldbeater's skin is the prepared outside membrane of the large intesti ...

A device for measuring the frequency of occurrence of atmospherics whose intensity is greater than a predetermined level.

Programmable Read-Only Memory. Read-only memory which can be programmed by the user using a special hardware programmer.

A unit of energy equal to 101 ergs or to 0.2389 calories.

The amount of sky covered or concealed by clouds or obscuring phenomena. It is reported in tenths, so that 0.0 indicates a clear sky and 1.0 (or 10/10) indicates a completely covered sky. The following classifications are used in aviation weather observat ...

See radiation shield.

A hygrometer in which the rotation of the hygrometric element is a function of humidity.