A power supply which achieves its output regulation by means of one or more active power handling devices which are alternately placed in the "off" or "on" states. It is more efficient than linear supplies which vary the conduction of power devices to ach ...

The transmission of data collected at a remote location over communications channels to a central station.

Any meteorological instrument, such as a radiosonde, in which the recording apparatus is located at some distance from the measuring apparatus.

(1) The ratio of the speeds of a chemical reaction at two temperatures differing by 10

An instrument used to measure and record earthquake vibrations and other earth tremors.

The maximum distance, usually horizontally, at which a given object or light source is just visible under particular conditions of transmittance and background luminance.

The change in a performance characteristic caused by a change in a specified operating condition from reference operating condition, all other conditions being held within the limits of reference operating conditions.

The officially designated elevation of an airport above mean sea level, taken as the highest point on any of the runways of the airport. Same as airport elevation.

Wind with a speed between 48 and 55 knots (55 and 63 mph), Beaufort scale number 10.

A halo phenomenon consisting of a horizontal circle passing through the moon, corresponding to the parhelic circle through the sun. Produced by reflection of moonlight from ice crystals.

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

A recording weight barometer.

Precipitation falling from a cloud, usually in wisps or streaks, but evaporating before it reaches the ground.

A temperature-sensing element which converts thermal energy directly into electrical energy. In its basic form it consists of two dissimilar metallic conductors connected in a closed loop. Each junction forms a thermocouple. If one thermocouple is maintai ...

A mercury barometer which measures atmospheric pressure by weighing the mercury in the column or cistern.

Any twelve-month period, usually selected to begin and end during a relative dry season. Used a basis for processing streamflow and other hydrologic data. The period from October 1 to September 30 is widely used in the U.S.

The attenuation of light.

A component of the wind (often using Cartesian coordinates. i.e. X and Y wind vectors). Also, an arrow representing wind velocity, drawn to point in the direction of the wind and with a length proportional to wind speed.

That part of an audio-modulated radiosonde consisting of the baroswitch, the sensing elements, the reference elements, and the relay.

The interval between the lower and upper measuring limits of an instrument, i.e. a thermometer with a range of -35 to 50