An instrument for measuring the intensity of light or the relative intensity of a pair of lights. Also called an illuminometer. If the instrument is designed to measure the intensity of light as a function of wavelength, it is called a spectrophotometer. ...

An up slope wind due to local surface heating. Opposite of katabatic wind.

A graphical aid used in fire weather forecasting to calculate the degree of forest-fire danger (or burning index). Commonly in the form of a circular slide rule, the firedanger meter relates numerical indices of (a) the seasonal stage of foliage, (b) the ...

An instrument which automatically records the voltage applied to it, as a function of time.

A hygrometer based upon the diffusion of water vapor through a porous membrane.

A self-recording psychrometer.

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.

Instrument for measuring the intensity of radiant energy. Its principle is based on the variation of electrical resistance, with the incoming radiation, of one or both the metallic strips which the instrument comprises.

The frequency of a carrier wave.

A contact anemometer connected to an electrical circuit which is so arranged that the average wind speed is indicated.

The correctable part of the inaccuracy of an instrument.

See photometer.

The ratio of the output of an instrument to the input value, i.e. a rain gauge with a sensitivity of 1 tip per 0.01"

The total area drained by a river and its tributaries. Same as watershed.

A small anemometer with flat vanes which indicates the number of linear feet or meters of air which have passed the instrument during its exposure.

The range through which the input may be varied without initiating a response. Usually expressed as a percentage of full-scale range.

Difference between the instantaneous wind velocity at a point and the mean wind velocity taken over a given time interval. Also called fluctuation velocity.

A device that allows a terminal or computer at one location to communicate with a terminal or computer at a distant location via wire or phone lines.

Thermodynamic change of state of a system in which there is transfer of heat across the boundaries of the system. Compare to adiabatic process.

A standard unit of atmospheric pressure, defined as the pressure exerted by a 760 mm column of mercury at standard gravity (980.665 cm/sec2 ) at O