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

A motorlike device containing a rotor and a stator and capable of converting an angular position into an electrical signal, or an electrical signal into an angular position. When several synchros are correctly connected, all of the rotors will align thems ...

An area of low atmospheric pressure which has a closed circulation that is cyclonic (counterclockwise in northern hemisphere and clockwise in southern hemisphere).

A sudden, significant increase in station pressure.

An aneroid barograph designed to record atmospheric pressure variations of very small magnitude.

General name for an instrument which measures the evaporation rate of water into the atmosphere. See clay atmometer, evaporation pan, evapotranspirometer, Livingston sphere, Piche evaporimeter, radio atmometer.

A balloon designed to float at a constant pressure level. This may be accomplished by a pressure valve which controls the release of ballast so as to maintain flight above a selected pressure level until the supply of ballast is exhausted. See Moby Dick b ...

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 ...

As used by the U.S. Army Corps of Engineers, the departure (in

For a given locality and month, an empirical expression devised for the purpose of classifying climates numerically on the basis of precipitation and evaporation.

An instrument resulting from the combination of a thermograph and a hygrograph and furnishing, on the same chart, simultaneous time recording of ambient temperature and humidity.

A barometer which measures atmospheric pressure using one or a series of aneroid capsules. Also called holosteric barometer.

Situated on the side from which the wind blows.

That portion of the record of a microbarograph between any two (or a specified small number) of successive crossings of the average pressure level (in the same direction). Analogous to microseism.

National Centers for Environmental Prediction. Central computer and communications facility of the National Weather Service; located in Washington, DC.

The pressure unit of the meter-ton-second system of physical units. equal to 10 millibars or 101 dynes per cm2.

Growth of a cloud or precipitation particle by the collision and union of a frozen particle with a super-cooled water drop.

Technically, the temperature registered by the dry-bulb thermometer of a psychrometer. However, it is identical with the temperature of the air and may also be used in that sense.

A thermometer with a muslin-covered bulb which is moistened. used to measure wet-bulb temperature.

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