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.

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 Sunshine recorder of the type in which the time scale is supplied by the motion of the sun. The instrument, which is pointed at the celestial pole, consists of a hemispherical mirror mounted externally on the optical axis of a camera. The lens of the ca ...

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

Name sometimes given to a transmissometer.

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.

Same as freezing point.

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

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

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 ...

See evaporation pan.

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.

Infrared radiation emitted by or being propagated through the atmosphere.

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

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

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.

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

Same as wind sock.

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

See calorie.