Same as windsock.

A type of precipitation composed of unbranched crystals in the form of needles, columns, or plates. Usually has a very slight downward motion and may fall from a cloudless sky.

A photometer that measures the received intensity of a distance tight source.

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

An absolute pyhrliometer, developed by C.G. Abbott, in which the radiation-sensing element is a blackened water-calorimeter.

Same as radiation pattern. Anticyclone-An area of high atmospheric pressure which has a closed circulation that is anticyclonic (clockwise in northern hemisphere and counterclockwise in southern hemisphere).

An instrument which determines the black-body temperature of a substance by measuring its thermal radiation.

Any sudden and heavy rain, almost always of the shower type.

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.

A instrument designed to study small fluctuations of some quantity. The microbarograph is an example of a recording pressure variometer.

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.

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 ...

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

See hydrologic accounting.

A graphical device used for the determination of the speed of the geostrophic wind from the isobar or contour-line spacing on a synoptic chart.

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.

Conditions to which a device is subjected, not including the variable measured by the device. See normal operating conditions, reference operating conditions.

An old nautical term for mercury barometer.