An ion counter of the aspiration condenser type, used for the measurement of the concentration and mobility of small ions in the atmosphere.

An instrument which measures evaporation by measuring the loss of water from a burette reservoir through a ceramic disc.

The number of cycles per second between the limits of a frequency band.

See Koschmieder's law.

A measure of the relative power, or of the relative values of two flux densities, especially of sound intensities and radar power densities. The decibel is derived from the less frequently used unit, the bel, named in honor of Alexander Graham Bell.

The limiting values of ceiling, visibility, and wind, or runway visual range, established as safety minimum for aircraft landings and take-offs.

An up slope wind due to local surface heating. Opposite of katabatic wind.

Old snow that has become granular and compacted as a result of melting and refreezing.

Very generally, any moving- stream of air. It has no particular technical connotation.

An ice coating with a consistency intermediate between glaze and rime.

Instrument for measuring the depth to which the soil is frozen.

The amount of precipitation captured by a rain gauge.

An automatic, recording cloud height indicator.

Pertaining to measurements or devices in which the output varies continuously, i.e. voltage or rotation signals. Compare to digital.

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

A small anemometer with flat vanes which indicates the number of linear feet or meters of air which have passed the instrument during its exposure.

See aneroid capsule.

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

A device for obtaining a continuous record of stage at a point on a stream. The most common recorders consist of a float-actuated pen which traces a record on a clock driven chart.

Formation of a single water drop by the union of two or more colliding drops.