An instrument for measuring the relative speed of a fluid. It consists of a concentric pipe arrangement in which the inner pipe is open at one end and the outer pipe is perforated and closed at both ends. Each pipe is connected to a manometer. The unit is ...

The time required for an instrument to register a designated percentage (frequently 90%) of a step change in the variable being measured.

Amount of solar radiation incident, per unit area and time, on a surface which is perpendicular to the radiation and is situated at the outer limit of the atmosphere, the earth being at its mean distance from the sun. It equals approximately 2.00 ly/ min ...

An elongated area of relatively low atmospheric pressure. Usually associated with and most clearly identified as an area of maximum cyclonic curvature of the wind flow. The opposite of a ridge.

A defective maximum thermometer of the liquid-inglass type in which the mercury flows too freely through the constriction. Such a thermometer will indicate a maximum temperature that is too low.

A buoyant balloon rising freely in the atmosphere, as opposed to a captive balloon.

The lowest value of a measured quality at which a sensor meets its accuracy specification.

A pyrheliometer of the bimetallic type used to measure the intensity of direct solar radiation.

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

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

See hurricane beacon.

A unit of energy equal to 1.356joules.

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

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

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

A relatively small-scale, downward moving current of air.

A line drawn through geographical points having the same duration of sunshine (or other function of solar radiation) during a given interval of time.

An instrument for measuring snow hardness in terms of the resistance of snow to the pressure exerted by a disk attached to a spring-loaded rod, a gauge calibrated in pounds per square inch registers the amount of resistance. See Canadian hardness gauge.

That stage, on a fixed river gauge, at which overflow of the natural banks of the stream begins to cause damage in any portion of the reach for which the gauge is used as an index.