A curve showing the variation of temperature with height in the free air. See lapse rate.

A conductor or system of conductors for radiating and/or receiving radio energy. Also called aerial.

A refraction phenomenon similar to a parahelion, but occurring generally at a distance of 120

The distance that an observer can see vertically into a surface-based obscuring phenomenon such as fog, rain, or snow. The distance estimate must be based upon ceiling balloon ascensions or ceiling light projector measurements.

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

A tube designed to measure the rate of flow of fluids. It consists of a tube having a constriction or throat at its midsection. The difference between the pressure measured at the inlet and at the throat is a function of the fluid velocity. Compare to Pit ...

A thermometer with a muslin-covered bulb which is moistened. used to measure wet-bulb temperature.

The upper surface of a column of liquid.

An instrument for determining the direction of cloud motion. There are two basic designs of nephoscope, the directvision nephoscope and the mirror nephoscope.

A cup anemometer with its shaft mechanically coupled to a magneto.

NEXt Generation RADar. A NWS network of about 140 Doppler radars operating nationwide.

The depth of water that would result from the melting of snow or ice, assuming measurement on a horizontal surface and no infiltration or evaporation.

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

A wooden enclosure about sixteen feet square and eight feet high with a precipitation gauge at its center. The function of the fence is to minimize eddies around the gauge and thus insure a catch that is representative of the actual rainfall or snowfall.

The change in the measured transducer output caused by changes in ambient temperature. Usually expressed a percentage of full scale.

The attenuation of light.

The minimum temperature shown by a minimum thermometer exposed in an open situation with its bulb at the level of the tops of the grass blades of short turf.

A contact anemometer connected to an electrical circuit which is so arranged that the average wind speed is indicated.

The gravity flow of water within soil.

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.