See photometer.

A seasonal wind of persistent direction, characterized by a pronounced change in direction between seasons.

A small balloon used to determine the height of the cloud base. The height can be computed from the ascent velocity of the balloon and the time required for its disappearance into the cloud.

The height at which the maximum wind speed occurs, determined in a winds-aloft observation.

See hook gauge.

A rain gauge capable of measuring very small amounts of precipitation. Also called micropluviometer, trace recorder.

A mercury barometer which measures atmospheric pressure by weighing the mercury in the column or cistern.

A radiosonde which is dropped by parachute from an aircraft for the purpose of obtaining soundings of the atmosphere below.

The audio-frequency signal transmitted by the Diamond-Hinman radiosonde when the baroswitch pen passes each fifteenth contact of the commutator, up to a number determined by the design of the commutator, and each fifth contact thereafter. This signal is t ...

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.

The programs and instructions which direct a computer.

An elongated area of relatively low atmospheric pressure. Usually associated with and most clearly identified as an area of maximum cyclonic curvature of the wind flow. The opposite of a ridge.

Apparatus designed to measure and record the size distribution of raindrops as they occur in the atmosphere.

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

Same as aneroid barometer. Holostelic means wholly made of solids, while aneroid means devoid of liquid.

Psychrometer to which a small chain or rotary handle is attached so that the observer can rotate the instrument rapidly to properly ventilate the thermometer bulbs.

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

The time required for an instrument to register a designated percentage (frequently 90%) of a step change in the variable being measured.

Contraction for radiosonde observation.

A feeble oscillatory disturbance of the earth's crust, detectable only by very sensitive seismographs. Certain types of microseisms seem to be closely correlated with pressure disturbances. See microbarm.