A rocket designed primarily for routine upper air observations in the lower 250,000 feet of the atmosphere, especially that portion inaccessible to balloons (above 100,000 feet).

Binary Coded Decimal. A coding system in which each decimal digit from 0 to 9 is represented by a 4-digit binary number.

Ice crystal deposits formed by sublimation (conversion of water vapor directly to ice) when temperature and dew point are below freezing.

A rainbow formed by light rays which have been reflected from an extended water surface. Not to be confused with a reflected rainbow whose image may be seen in a still body of water. The center of a reflection rainbow is at the same elevation as the sun b ...

An instrument for measuring the difference of the solar radiation falling on both sides of a horizontal surface from the whole hemisphere.

An instrument used to determine atmospheric pressure or elevation by observing the boiling point of water or both liquids. The sensitivity of the hypsometer increases with decreasing pressure, making it more useful for high altitude work.

Snow gauge composed of a metal cylinder, closed at one end, used to obtain a sample of snow from which the water is measured after melting.

A measure of luminous flux remaining in a light beam after it has passed through a specified distance of the atmosphere.

A point (or line) on a scale used for reference or comparison purposes. In calibration of meteorological thermometers, for example, the fiducial points are 100

A pyrheliometer of the bimetallic type used to measure the intensity of direct solar radiation.

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

A thin metal disc partially evacuated of air used to measure atmospheric pressure by measuring its expansion and contraction.

A recording hair hygrometer.

A type of disk hardness-gauge, especially useful in relatively soft snow. See disk hardness gauge.

A line of equal or constant pressure.

In the direction from which the wind is blowing.

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.

A contact anemometer connected to an electrical circuit which is so arranged that the average wind speed is indicated.

Thermometer in which the difference in the rates of expansion with temperature of a liquid and its receptacle is used as a measure of the temperature. The liquid used may be ethyl alcohol, toluene, petroleum, or mercury.

A device that allows a terminal or computer at one location to communicate with a terminal or computer at a distant location via wire or phone lines.