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

A unit of signaling speed representing the number of code elements sent per second; often, bits per second.

February 2nd. In American folklore, a day that is popularly supposed to provide the key to the weather for the remainder of the winter. Specifically, if the ground-hog upon emerging from its hole casts a shadow, it will return underground, thereby forebod ...

A definite portion of a stream channel, commonly taken between two gauging stations, but may be taken between any two specified points.

The amount of precipitation captured by a rain gauge.

The range through which the input may be varied without initiating a response. Usually expressed as a percentage of full-scale range.

A numbering system using a base number of 2 and having only two digits: 0 and 1. The fundamental system of representing information with electrical pulses.

The array of indicating marks and figure in relation to which the position of an index is observed, i.e. a scale plate on a recorder.

Abbreviation for visual flight rules, but commonly used to refer to the relatively favorable weather and/or flight conditions to which these rules apply.

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 ...

A modification of the dew cell used in radiosonde equipment.

A device which converts energy from one form into another, i.e. an ac generator transducer which converts the mechanical motion of anemometer cups into an electrical signal.

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.

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.

See ceilometer.

A radiosonde whose carrier wave is switched on and off in such a manner that the interval of time between the transmission of signals if a function of the magnitude of the meteorological elements being measured.

The point (physical and/or electrical) where two distinct data processing elements meet.

That horizontal wind velocity at which the Coriolis acceleration exactly balances the horizontal pressure force. It is directed along contour lines or isobars.

A thermometer, invented by James Six in 1782, which simultaneously indicates the maximum and minimum temperatures attained during a given interval of time. A U-tube min/max thermometer

The part of a measuring instrument which responds directly to changes in the environment.