An instrument designed to measure the effect of sunlight on evaporation from plant foliage. It consists of a porous clay atmometer whose surface has been blackened so that it absorbs radiant energy.

The algebraic difference between the upper and lower limits of the measuring range of an instrument, i.e. a thermometer with a range of -35 to 50

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.

The range of operating conditions of a device within which operating influences are negligible. The range is usually narrow. Reference operating conditions are the conditions under which reference performance is stated and the base from which the values o ...

See stage.

An atmometer consisting of a porous porcelain or ceramic container connected to a calibrated reservoir filled with distilled water. Evaporation is determined by the depletion of water in the reservoir.

Reduction of visibility by strong winds blowing across dry ground with little or no vegetation. Visibilities of 1/8 mile or less over a widespread area are criteria for a Blowing Dust Advisory.

Operation mode of a communication circuit in which each end can transmit and receive, but not simultaneously.

See hydrologic accounting.

Same as wave pole.

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

Same as atmospheric pressure.

General term for an instrument used to make direct measurements of visual range or measurements of the physical characteristics of the atmosphere which determine the visible range.

A thermometer which uses a transducing element whose element proper-ties are a function of its thermal state. Common meteorological examples of such thermometers are the resistance thermometer and the thermoelectric thermometer.

The attenuation of light.

In Jeffreys' classification, a wind for which the pressure force exactly balances the viscous force, in which the vertical transfers of momentum predominate.

A photoelectric spectrophotometer which is used in the determination of the ozone 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.

The audio-frequency signal transmitted by the Diamond-Hinman radiosonde when the baroswitch pen passes each fifth contact of the commutator up to a number determined by the design of the commutator. It then signals every contact except the fifth, which is ...

A unit of luminance or brightness equal to 1/d candles per foot'.