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

A faintly-colored circular arc similar to a rainbow but formed on fog layers containing drops whose diameters are 100 microns or less. Also called mistbow, white rainbow.

Automated Surface Observing System. A network of instrumented weather stations deployed primarily by the National Weather Service to make weather observations without operator involvement.

The pressure unit of the meter-ton-second system of physical units. equal to 10 millibars or 101 dynes per cm2.

A transducer which converts electromagnetic radiation in the infrared, visible, and ultraviolet regions into electrical quantities such as voltage, current, or resistance. Also called photo cell.

Conditions to which a device is subjected, not including the variable measured by the device. See normal operating conditions, reference operating conditions.

A fixed support for mounting maximum and minimum thermometers of the liquid-in-glass type. The support holds the thermometers at the correct operating attitude and also permits their rotation for resetting when desired.

A thermoelectric thermometer used for measuring air temperature. The name is derived from the fact that the reference thermocouple is placed in an insulated bottle.

An instrument for determining the direction of cloud motion. There are two basic designs of nephoscope, the directvision nephoscope and the mirror nephoscope.

The process whereby a position on the scale of an instrument is identified with the magnitude of the signal (or input force) actuating the instrument.

The inaccuracy that the manufacturer permits when the unit is calibrated in the factory.

The unit of force in the centimeter-gram-second system of physical units, i.e. one gm cm per sec2, equal to 7.233 x 10-5 poundal.

Frozen or partly frozen rain.

In folklore, a name for wind.

A high-altitude sounding system consisting of a small solid- propellant research rocket carried aloft by a large plastic balloon. The rocket is fired near the maximum altitude of the balloon flight.

Same as mercury barometer.

Name applied to a class of instruments which measure the liquid content of the atmosphere.

The degree of conformity of an indicated value to an accepted standard value, or ideal value. See accuracy rating, measured accuracy.

Central Processing Unit. The part of a computer which controls and directs all functions.

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