An atmometer which uses a filter paper disc as the evaporating element. The amount of water evaporated through the paper is read at the graduated tube reservoir.

Same as pitot tube.

An instrument that shows changes in humidity.

A set of regulations set down by the U.S. Civil Aeronautics Board to govern the operational control of aircraft on instrument flight. The abbreviation of this term is seldom used to denote the rules themselves, but is in popular use to describe the weathe ...

Same as photometer.

See feed.

A pyrheliometer of the thermoelectric type. Radiation is allowed to fall on two concentric silver rings, the outer covered with magnesium oxide and the inner covered with lamp black. A system of thermocouples (thermopile) is used to measure the temperatur ...

A hydrometeor consisting of a visible aggregate of minute water and/or ice particles in the atmosphere above the earth's surface. Cloud differs from fog only in that the latter is, by definition, in contact with the earth's surface.

A modification of the dew cell used in radiosonde equipment.

Forecasting weather by the use of numerical models, run on high speed computers. Most of the NWP for the National Weather Service is done at the National Centers for Environmental Prediction (NCEP).

A radar which is used to obtain the azimuth elevation, and slant range of an airborne target.

A number of quantity defining a limit that errors will not exceed when a device is used under specified operating conditions. Accuracy rating can be expressed in a number of forms, i.e. in terms of the measured variable (+/- 1 C), percent of span (+/-0.5% ...

The audio-frequency signal transmitted by the Diamond-Hinman radiosonde when the baroswitch pen passes each fifteenth contact of the commutator, up to a number determined by the design of the commutator, and each fifth contact thereafter. This signal is t ...

An evaporation pan in which the evaporation is measured from water in a pan floating in a larger body of water.

A radiosonde which is dropped by parachute from an aircraft for the purpose of obtaining soundings of the atmosphere below.

The flux of visible radiation, so weighted as to account for the manner in which the response of the human eye varies with the Wavelength of radiation. The basic unit for luminous flux is the lumen,

A sunshine recorder of the type in which the time scale is supplied by the motion of the sun. It consists essentially of a spherical lens which bums an image of the sun upon a specialty prepared card.

A graphical device used for the determination of the speed of the geostrophic wind from the isobar or contour-line spacing on a synoptic chart.

The array of indicating marks and figure in relation to which the position of an index is observed, i.e. a scale plate on a recorder.

An instrument resulting from the combination of a thermograph and a hygrograph and furnishing, on the same chart, simultaneous time recording of ambient temperature and humidity.