The total area drained by a river and its tributaries. Same as watershed.

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

Board that holds graph paper on which is plotted information obtained from a pilot-balloon observation.

See foehn.

meter-An instrument for measuring the transmissivity of the atmosphere; a type of transmissometer. It consists of a constant- intensity collimated light source located at a suitable distance from a photoelectric cell. Variation in the turbidity of the atm ...

A white disk 12" or more in diameter which is lowered into the sea to estimate transparency of the water. The depths are noted at which it first disappears when lowered and reappears when raised.

in United States weather observing practice, the highest "instantaneous" wind speed recorded at a station during a specified period, usually the 24-hour observation day. Therefore, a peak gust need not be a true gust of wind.

An atmospheric phenomenon, other than clouds, which obscures a portion of the sky from the point of observation. Also called obscuration.

Abbreviation for binary digit. The smallest unit of information, equal to one binary decision, i.e. 1/0, on/off, yes/no.

Phase Shift Keying. A form of phase modulation of a data signal performed by a modem for transmission over dedicated wire or phone lines.

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

The standard deviation (positive square-root of the variation) of the errors associated with physical measurements of an unknown quantity, or statistical estimates of an unknown parameter or of a random variable.

Precipitation caused by the ascent of moist air over an orographic barrier such as a Mountain range.

An instrument for measuring differences of electric potential.

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

A device for measuring sea-surface waves. It consists of a weighted pole below which a disk is suspended at a depth sufficiently deep for the wave motion associated with deepwater waves to be negligible. The pole will then remain nearly as if anchored to ...

A balloon used to carry a radiosonde aloft, considerably larger than pilot balloons or ceiling balloons.

An instrument which measures the intensity of radiation by determining the amount of chemical change( or fluorescence produced by that radiation.

A colloquial term in western Australia for a squall, associated with thunder, on the northwest coast in summer.

Transistor-Transistor Logic.