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

A line of equal or constant pressure.

A mercury-in-glass thermometer which records the temperature upon being inverted and retains its reading until being returned to the first position.

Board that holds graph paper on which is plotted information obtained from a pilot-balloon observation.

A unit of energy equal to 1.356joules.

A type of anemometer in which the rotation of an element serves to measure the wind. Rotation anemometers are divided into two classes; those in which the axis of rotation is horizontal, such as the windmill anemometer, and those in which the axis of rota ...

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

See constant-level balloon.

A device, similar to a phytometer, for measuring transpiration. It consists of a small vessel containing water and sealed so that the only escape of moisture is by transpiration from a leaf, twig, or small plant with its cut end inserted in the water.

An instrument used to measure the water vapor content of the air. A type of hygrometer. It consists of a wet-bulb and a dry-bulb thermometer. See aspiration psychrometer, Assmann psychrometer. hygrodeik, sling psychrometer.

A measure of long-term precipitation effectiveness. The ratio of the normal annual rainfall to the normal annual evaporation.

The boundary between the troposphere and stratosphere, usually characterized by an abrupt change in lapse rate. Its height varies from 10 to 20 km. Regions above the tropopause have greater atmospheric stability than regions below.

Phase Shift Keying. A form of phase modulation of a data signal performed by a modem for transmission over dedicated wire or phone lines.

A type of electrical thermometer in which the thermal element is a substance whose electrical resistance varies with the temperature. Such thermometers can be made with very short time constants and are capable of highly accurate measurements.

A general term for atmospheric water in any of its forms, i.e. clouds, fog, hail, ice crystals, rain.

The actual lifting force of an inflated balloon, usually expressed in grams.

A systematic summary of the terms (inflow, outflow, and storage) of the storage equation as applied to the computation of soil-moisture changes, ground-water changes, etc. An evaluation of the hydrologic balance of an area. Also called basin accounting, w ...

A device for measuring the river stage. Also called stream gauge.

A large plastic constant-level balloon for duration flying (in excess of 24 hours) at altitudes above 40,000 feet, used for the determination of wind fields and the measurement of upper atmospheric parameters.

The total amount of water transferred to the atmosphere by evapotranspiration.