The volume of water required to cover one acre to a depth of one foot: 43,560 cubic feet.

A momentary decrease in the speed of the wind.

A systematic summary of the terms (inflow, outflow, and storage) of the storage equation as applied to the computation of soil-moisture changes, ground-water changes, etc. An evaluation of the hydrologic balance of an area. Also called basin accounting, w ...

Determination of the total amount of snow covering a watershed or a given region. Both depth and water content of the snow may be measured, and the results may be used to predict the amount of water that will be available after melting.

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

Barometer in which pressure is determined by balancing air pressure against the weight of a column of mercury in an evacuated glass tube.

A large body of air having similar horizontal temperature and moisture characteristics.

Snow shower, particularly of a very light and brief nature.

An instrument which measures the spectral distribution of the intensity of direct solar radiation.

Liquid water at temperatures colder than freezing.

Same as mirror nephoscope.

An instrument which determines the black-body temperature of a substance by measuring its thermal radiation.

An instrument used to measure changes in the level of the water in an evaporation pan. The gauge is normally placed in a Stillwell and adjusted so that the point of the hook just breaks the water surface. The change in water level is read on the attached ...

See hurricane beacon.

A rain gauge capable of measuring very small amounts of precipitation. Also called micropluviometer, trace recorder.

A hygrometer which uses a transducing element whose electrical properties are a function of atmospheric water vapor content. The humidity strip and carbon-film hygrometer element are examples of such a transducer.

A system of estimating and reporting wind speed, originally based on the effect of various wind speeds on the amount of canvas that a full-rigged nineteenth century frigate could carry.

A unit of energy defined as the heat required to raise the temperature of one pound of water one degree Fahrenheit. It is equal to 252.1 calories or to 1055 joules.

A device for measuring the frequency of occurrence of atmospherics whose intensity is greater than a predetermined level.

Upwarddirected solar radiation, reflected by the earth's surface and the atmosphere.