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.

A modification of the dew cell used in radiosonde equipment.

An anemometer which measures wind speed by means of the properties of wind-borne sound waves. It operates on the principle that the propagation velocity of a sound wave in a moving medium is equal to the velocity of sound with respect to the medium plus t ...

A mercury barometer in which the lower mercury surface is larger in area than the upper surface. The basic construction of a cistern barometer is as follows: A glass tube one meter in length, sealed at one end is filled with mercury, and then inverted. Th ...

An up slope wind due to local surface heating. Opposite of katabatic wind.

An instrument which measures the effective terrestrial radiation. See Angstrom pyrgeometer.

Precipitation composed of balls or irregular lumps of ice with diameters between 5 and 50 mm.

Wind with a speed between 4 and 6 knots (4 and 7 mph), Beaufort scale number 2.

An instrument which records the duration of sunshine and gives a quantitative measure of the amount of sunshine by the action of the sun's rays upon blueprint paper. A type of sunshine recorder.

Video Display Terminal. An input and display device which includes a keyboard and a screen and allows a human to communicate with a computer.

An absolute instrument developed by K. Angstrom for the measurement of direct solar radiation. The radiation receiver station consists of two identical manganin strips whose temperatures are measured by attached thermocouples. One of the strips is shaded, ...

A self-recording psychrometer.

Generally, a measure of the departure of the mean daily temperature from a given standard, one degree day for each degree (

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.

An aviation weather forecast for a specific flight.

Meteorological information issued by a watch office concerning the occurrence or forecast of weather phenomena which may affect the safety of aircraft operations.

A large plastic constant-level balloon for duration flying (in excess of 24 hours) at altitudes above 40,000 feet, used for the determination of wind fields and the measurement of upper atmospheric parameters.

A conductor or system of conductors for radiating and/or receiving radio energy. Also called aerial.

A thermopile used in some types of radiation instruments. See solarimeter.

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.