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.

See photometer.

An addition to a rawinsonde system which allows determination of the slant range to the radiosonde.

See hurricane beacon.

A rotation anemometer which has a horizontal axis upon which helicoidal shaped vanes are mounted. See windmill anemometer.

See foehn.

A forecast of the expected stage or discharge at a specified time, or of the total volume of flow within a specified Interval of time, at one or more points along a stream.

A line of equal or constant temperature.

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.

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

The total electromagnetic radiation emitted by the sun. About 99.9 percent of its energy output falls within the wavelength interval from 0. 15 microns to 4.0 microns, with peak intensity near 0.47 microns. About one-half of the total energy in the solar ...

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.

Winds which, over a small area, differ from those which would be appropriate to the general pressure distribution.

A device for computing certain psychrometric data, usually the dew point and the relative humidity, from known values of the dry-bulb and wet-bulb temperatures and the atmospheric pressure. One type is the circular slide-rule form and, like the psychromet ...

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

An effect noted primarily in wet snow conditions when snow clings to the sides of a precipitation gauge and gradually accumulates until the gauge orifice is capped with accumulated snow. This effect can be minimized by using large collectors, and wind scr ...

A magnetometer of the electromagnetic type which is used to measure the horizontal intensity of the earth's magnetic field.

A photometer which measures the intensity of radiation as a function of the frequency (or wavelength) of the radiation.

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.