Thermometer used for measuring the highest temperature attained during a given interval of time, for example, a day.

See evaporative opportunity.

The line-of-sight distance between two objects.

An instrument for measuring the extinction coefficient in water.

A measure of the intrinsic luminous intensity emitted by a source in a given direction. Luminance is a measure only of light. The comparable term for electromagnetic radiation in general is radiance.

An element that can control current without moving parts, heated filaments, or vacuum gaps.

General term for any device that measures precipitation: principally a rain gauge or snow gauge.

The difference between temperature measurements taken at two significant levels above the ground. Temperatures at 10 and 40 meters are commonly used.

A metallic element of atomic weight 200.6 1, unique (for metals) in that it remains liquid under all but very extreme temperatures.

The maximum positive and negative deviation observed in testing a device under specified conditions and by a specified procedure. It is usually measured as an inaccuracy and expressed as accuracy, typically in terms of the measured variable, percent of sp ...

Radio Direction Finder.

The source of illumination for an antenna reflector. Also called antenna feed.

The direction, with respect to true north, from which the wind is blowing. Distinguish from magnetic wind direction. In all standard upper-air and surface weather observations, it is true wind direction that is reported.

A temperature scale on which the freezing point of water equals 32

A device which automatically records the water equivalent of snow on a given surface as a function of time. A small sample of a radioactive salt is placed in the ground in a shielded collimator which directs a beam of radioactive particles upwards. A Geig ...

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.

The direction, with respect to magnetic north, from which the wind is blowing. Distinguish from true wind direction.

Same as Aeolian.

That portion of the atmosphere which is above the lower troposphere. Generally applied to levels above 850 mb.

The amount of moisture which, if available, would be removed from a given land area by evapotranspiration. Expressed in units of water depth.