An anemometer which derives wind speed from measurements of dynamic wind pressures. Wind blowing into a tube develops a pressure greater than the static pressure, while wind blowing across a tube develops a pressure less than the static. This pressure dif ...

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

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 ...

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.

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 ...

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.

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

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

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

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

A unit of energy equal to 1.356joules.

See hurricane beacon.

A seasonal wind of persistent direction, characterized by a pronounced change in direction between seasons.

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.

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

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

An atmometer which uses a filter paper disc as the evaporating element. The amount of water evaporated through the paper is read at the graduated tube reservoir.