The maximum distance along the runway at which the runway lights are visible to a pilot at touchdown. Runway visual range may be determined by an observer located at the end of the runway, facing in the direction of landing, or by means of a transmissomet ...

A balloon designed to float at a constant pressure level. This may be accomplished by a pressure valve which controls the release of ballast so as to maintain flight above a selected pressure level until the supply of ballast is exhausted. See Moby Dick b ...

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.

Solar and terrestrial radiation directed upward (away From the earth's surface); outgoing radiation.

Same as freezing point.

See evaporation pan.

An instrument for measuring angles of inclination. Used in conjunction with a ceiling light to measure cloud height at night.

A relatively small-scale, upward moving current of air.

A colloquial term in western Australia for a squall, associated with thunder, on the northwest coast in summer.

The ratio of the amount of electromagnetic radiation reflected by a body to the amount incipient upon it, commonly expressed as a percentage. The albedo is to be distinguished from the reflectivity, which refers to one specific wavelength.

A temperature scale with the ice point at 273 degrees and boiling point of water at 373 degrees. It is intended to approximate the Kelvin temperature scale with sufficient accuracy for many sciences, notably meteorology.

Name sometimes given to a transmissometer.

The envelope of air surrounding the earth and bound to it more or less permanently by virtue of the earth's gravitational attraction. The system whose chemical Properties. dynamic motions, and physical processes constitute the subject matter of meteorolog ...

Infrared radiation emitted by or being propagated through the atmosphere.

Same as wind sock.

A unit of energy equal to 101 ergs or to 0.2389 calories.

See calorie.

Interational thermometric scale on which the freezing point of water equals 0

The older name for the Celsius temperature scale. Officially abandoned by international agreement in 1948, but still in common use.

A thermoelectric thermometer used for measuring air temperature. The name is derived from the fact that the reference thermocouple is placed in an insulated bottle.