The lowest temperature that can be obtained on a wet-bulb thermometer in any given sample of air. Obtained by evaporation of water (or ice) from the muslin wick. Used in computing dew point and relative humidity.

An instrument for determining the direction from which radio waves approach a receiver. It may consist of a manually operated direction indicator, or it may use a servo system to position the antenna automatically in the direction of the incident waves. T ...

The line-of-sight distance between two objects.

A rotation anemometer which has a horizontal axis upon which helicoidal shaped vanes are mounted. See windmill anemometer.

Contraction for radiosonde observation.

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.

An elongated area of relatively low atmospheric pressure. Usually associated with and most clearly identified as an area of maximum cyclonic curvature of the wind flow. The opposite of a ridge.

The source of illumination for an antenna reflector. Also called antenna feed.

Snow gauge composed of a metal cylinder, closed at one end, used to obtain a sample of snow from which the water is measured after melting.

The state of the atmosphere, mainly with respect to its effects upon life and human activities. As distinguished from climate, weather consists of the short-term (minutes to months) variations of the atmosphere.

A particular pattern of snow sampler having an internal diameter of 1.485 inches so that each inch of water in the sample weighs one ounce.

A hydrostatic principle that pressure supplied to an enclosed fluid is transmitted undiminished to every portion of the fluid and to the walls of the containing vessel.

A unit of energy per unit area commonly employed in radiation theory. Equal to one gram-calorie per square centimeter.

Solar and terrestrial radiation directed upward (away From the earth's surface); outgoing radiation.

Air in motion relative to the surface of the earth. Almost exclusively used to denote the horizontal component.

The actual time during which physical events take place.

The process by which water in plants is transferred as water vapor to the atmosphere. Also, the amount of water so transferred.

A small, moveable graduated scale adjacent and parallel to the main scale of an instrument. It provides a means for interpolating between the graduations of the main scale.

A measure of long-term precipitation effectiveness. The ratio of the normal annual rainfall to the normal annual evaporation.

Same as instrument shelter.