A unit of mass numerically equal to the molecular weight of the substance. The gram-mote or gram-molecule is the mass in grams numerically equal to the molecular weight, i.e. a gram-mole of oxygen is 32 grams.

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

See radiation shield.

A type of pressure-tube anemometer, named after the inventor.

Same as precipitation-evaporation ratio.

The record or trace made by a microbarograph.

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 rotation anemometer in which the axis of rotation is horizontal. The instrument has either flat vanes (as in the air meter) or helicoidal vanes (as in the propeller anemometer). The relation between wind speed and angular rotation is almost linear.

General name for an instrument which measures the evaporation rate of water into the atmosphere. See clay atmometer, evaporation pan, evapotranspirometer, Livingston sphere, Piche evaporimeter, radio atmometer.

The water volume within a specified portion of a stream channel.

Anemometer whicb measures wind speed by measuring the degree of cooling of a metal wire heated by an electric current. A type of cooling power anemometer.

One of the radiation laws which states that the wavelength of maximum radiation intensity for a black body is inversely proportional to the absolute temperature of the radiating black body.

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

A type of instrument shelter. It is a wooden box painted white with double louvered sides and mounted on a stand four feet above the ground.

A halo consisting of a faint white circle passing through the Sun and running parallel to the horizon for as much as 360

One of several constant-pressure levels in the atmosphere for which a complete evaluation of data derived from upper air observations is required.

A rain gauge which indicates but does not record the amount of precipitation captured.

The pressure exerted by the atmosphere as a consequence of gravitational attraction exerted upon the "column" of air lying directly above the point in question.

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

For a given location, a measure of the long-range effectiveness of precipitation in promoting plant growth. Also called precipitation-evaporation index.