Abbreviation for visual flight rules, but commonly used to refer to the relatively favorable weather and/or flight conditions to which these rules apply.

A form of data transmission in which the bits of each character are sent one at a time along a single communication path. Compare to parallel data transmission.

(1) The initial component or the sensing element of a measuring system. For example, the receiver of a rain gauge is the funnel which captures the rain and the receiver of a thermoelectric thermometer is the measuring thermocouple. (2) An instrument used ...

The part of a measuring instrument which responds directly to changes in the environment.

A mercury barometer designed for use aboard ship. The instrument is of the fixed-cistern type (see Kew barometer). The mercury tube is constructed with a wide bore for its upper portion and with a capillary bore for its lower portion. This is done to incr ...

Generally, an instrument designed to measure or estimate the blueness of the sky. See Linke-scale.

A large body of air having similar horizontal temperature and moisture characteristics.

Same as windsock.

A white disk 12" or more in diameter which is lowered into the sea to estimate transparency of the water. The depths are noted at which it first disappears when lowered and reappears when raised.

A hypothetical, ideal body which absorbs completely all incident radiation. independent of wavelength and direction. No actual substance behaves as a true black body, although platinum black and other soots rather closely approximate this ideal. However, ...

A wave resulting from the action of wind on a water surface.

An increase in the central pressure of a pressure system; opposite of a deepening. More commonly applied to a low rather than a high.

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

See hydrologic accounting.

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

In physics, any process in which the flux density (or power, amplitude, intensity, illuminance, etc.) of a "parallel beam" of energy decreases with increasing distance from the source. Attenuation is always due to the action of the transmitting medium its ...

A method of upper air observation consisting of an evaluation of the wind speed and direction, temperature, pressure, and humidity aloft by means of a balloon-borne radiosonde tracked by radar or a radio theodolite.

Temperature to which absolutely dry air would have to be brought in order for it to have the same density as moist air, considered at the same pressure.

A unit of power equal to one joule per second or 10' ergs per second.

The state of the weather with respect to its effect upon the kindling and spreading of forest fires.