An approximation to the complete equations describing atmospheric motion in which only the terms most important for the growth and decay of synoptic scale extratropical weather systems (i.e., the large areas of high and low pressure seen on weather maps) ...

The total of all deviations of a transducer's output from a specified straight line in a constant environment.

The older name for the Celsius temperature scale. Officially abandoned by international agreement in 1948, but still in common use.

A common type of terrestrial scintillation; shimmering over a hot surface (such as a roadway) on a quiet, cloudless. summer day.

An instrument used to indicate wind direction.

General term for an instrument which records the vertical electric current in the atmosphere.

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.

Wind with a speed between 7 and 10 knots (8 and 12 mph), Beaufort scale number 3.

Interational thermometric scale on which the freezing point of water equals 0

Same as contact anemometer.

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

A general term for instruments designed to measure the amount of cloudiness.

Turbulence encountered by aircraft when flying through air space devoid of clouds. Thermals and wind shear are the main causes.

A thermograph in which ventilation is provided by a suction fan.

National Weather Service. Administered by the U.S. Department of Commerce.

Same as mirror nephoscope.

The ratio of the amount of electromagnetic radiation reflected by a body to the amount incipient upon it, commonly expressed as a percentage. The albedo is to be distinguished from the reflectivity, which refers to one specific wavelength.

See evaporation pan.

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.

Same as wind sock.