The size of the area comprising a watershed or river basin. Also called catchment area.

A unit of pressure which directly expresses the force exerted by the atmosphere. Equal to 1000 dynes/cm2 or 100 pascals.

Fine dust or salt particles dispersed through a portion of the atmosphere; a type of lithometer. The particles are so small they cannot be felt or seen with the naked eye. Many haze formations are caused by the presence of an abundance of condensation nuc ...

The programs and instructions which direct a computer.

A photoelectric spectrophotometer which is used in the determination of the ozone content of the atmosphere.

A method of winds aloft observation in which the elevation and azimuth angles of a theodolite are read while visually tracking a pilot balloon. Balloon height data is estimated from assumed balloon ascension rates.

See calorie.

An atmometer consisting of a porous porcelain or ceramic container connected to a calibrated reservoir filled with distilled water. Evaporation is determined by the depletion of water in the reservoir.

A thin metal disc partially evacuated of air used to measure atmospheric pressure by measuring its expansion and contraction.

A unit of luminous flux. The lumen is equal to the luminous flux radiated into a unit solid angle (steradian) from a small source having a luminous intensity of one candle. An ideal source possessing an intensity of one candle in every direction would rad ...

The mean difference between the readings of a given instrument and those of a standard instrument.

A buoyant balloon kept from rising freely by means of a line secured to a point on the ground, as opposed to a free balloon. See kytoon.

The sum of solar and terrestrial radiation.

An aneroid barometer with a scale graduated in altitude instead of pressure units.

In radiometry, a measure of the intrinsic radiant intensity emitted by a radiator in a given direction.

Same as instrument shelter.

The ceiling classification which is applied when the ceiling height is determined by timing the ascent and disappearance of a ceiling balloon or pilot balloon.

A unit of pressure used principally in oceanography. One decibar (10' dynes/cm2) equals 0.1 bar. In the ocean, hydrostatic pressure in decibars very nearly equals the corresponding depth in meters.

Lacking a relationship to a time base or clock. In asynchronous communications, individual data characters are sent at an arbitrary rate.

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