A systematic observational error due to the characteristics of the observer. The uncertainty in a reading made by an observer may be acertained by a statistical analysis of his or her readings.

An instrument which records the duration of sunshine and gives a quantitative measure of the amount of sunshine by the action of the sun's rays upon blueprint paper. A type of sunshine recorder.

A transducer for converting thermal energy directly into electrical energy. It is composed of pairs of thermocouples which are connected either in series or in parallel. Thermopiles are used in thermoelectric radiation instruments when the output of a sin ...

A relatively small-scale, upward moving current of air.

An instrument which measures the scattering function of particles suspended in a medium in order to determine the visual range through the medium. See visibility meter.

An old nautical term for mercury barometer.

The range through which the input may be varied without initiating a response. Usually expressed as a percentage of full-scale range.

An instrument which measures the effective terrestrial radiation. See Angstrom pyrgeometer.

See radiation shield.

The average temperature of the air as indicated by a properly exposed thermometer for a given time period, usually a day, a month, or a year.

Strong winds concentrated within a narrow band in the atmosphere. The jet stream often "steers" surface features such as front and low pressure systems.

Wind with a speed between 22 and 27 knots (25 and 31 mph); Beaufort scale number 6.

A pyrheliometer of the thermoelectric type. Radiation is allowed to fall on two concentric silver rings, the outer covered with magnesium oxide and the inner covered with lamp black. A system of thermocouples (thermopile) is used to measure the temperatur ...

A protocol similar to RS232 which makes use of differential transmission to provide high speed data transmission over significantly longer distances.

An instrument, for the recording of two or more meteorological parameters, in which the ventilation is provided by a suction fan.

An instrument for measuring the pressure of gases and vapors. A mercury barometer is a type of manometer.

A radiosonde whose carrier wave is modulated by audio-frequency signals whose frequency is controlled by the sensing elements of the instrument.

A remote indicator for wind speed and direction used in conjunction with a contact anemometer and a wind vane. The indicator consists of a center light, connected to the contact anemometer, surrounded by eight equally spaced lights which are individually ...

An area of low barometric pressure, with its attendant system of winds. Also called a depression or cyclone.

An instrument for rapidly obtaining samples of airborne dust; a type of dust counter. Particles pass through a cylindrical chamber, are drawn at high velocity through a narrow slit, and then impinge upon a microscope cover glass located a short distance f ...