Same as dropsonde.

An instrument whose calibration can be determined by means of simple physical measurements on the instrument. Compare to secondary instrument.

Operation mode of a communication circuit in which each end can transmit and receive, but not simultaneously.

An instrument, for the recording of two or more meteorological parameters, in which the ventilation is provided by a suction fan.

A type of electrical thermometer in which the thermal element is a substance whose electrical resistance varies with the temperature. Such thermometers can be made with very short time constants and are capable of highly accurate measurements.

Readily taking up and retaining moisture.

A photometer which measures the intensity of radiation as a function of the frequency (or wavelength) of the radiation.

A set of weekly colored rainbow arcs sometimes discernable inside a primary rainbow.

An instrument for the measurement of both solar and terrestrial radiation.

In the direction from which the wind is blowing.

Infrared radiation emitted by or being propagated through the atmosphere.

A device that combines several separate communications signals into one and outputs them on a single line.

Programmable Read-Only Memory. Read-only memory which can be programmed by the user using a special hardware programmer.

The distance that an observer can see vertically into a surface-based obscuring phenomenon such as fog, rain, or snow. The distance estimate must be based upon ceiling balloon ascensions or ceiling light projector measurements.

A type of instrument shelter. It is a wooden box painted white with double louvered sides and mounted on a stand four feet above the ground.

A high-altitude sounding system consisting of a small solid- propellant research rocket carried aloft by a large plastic balloon. The rocket is fired near the maximum altitude of the balloon flight.

An instrument which indicates the presence of precipitation. The ombroscope consists of a heated, water-sensitive surface which indicates by mechanical or electrical techniques the occurrence of precipitation.

A balloon having a detachable tail which is released when the balloon has undergone a predetermined expansion. It thus serves to measure approximately the density of the atmosphere at the point of release.

Sustained winds greater than or equal to 40 mph or gust greater than or equal to 58 mph.

Generally, an instrument designed to measure or estimate the blueness of the sky. See Linke-scale.