See photometer.

An instrument for determining the dust content of a sample of air. Also spelled conimeter.

A basic equation in daytime visual range theory, relating the apparent luminance of a distant black object, the apparent luminance of the background sky above the horizon, and the extinction coefficient of the atmosphere, or the air layer near the ground. ...

Random Access Memory. The memory of a computer which can be read and written into at any location without passing through preceding locations.

An air-launched balloon designed to be released in the eye of a tropical cyclone, float within the eye at predetermined levels, and transmit radio signals for RDF positioning.

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

Emission or transfer of energy in the form of electromagnetic waves or particles.

Similar to the spectroheliograph, but used for visual instead of photographic purposes.

See gust and peak gust.

The total area drained by a river and its tributaries. Same as watershed.

The audio-frequency signal transmitted by the Diamond-Hinman radiosonde when the baroswitch pen passes each fifteenth contact of the commutator, up to a number determined by the design of the commutator, and each fifth contact thereafter. This signal is t ...

Difference between the instantaneous wind velocity at a point and the mean wind velocity taken over a given time interval. Also called fluctuation velocity.

The scientific study of the waters of the earth, especially with relation to the effects of precipitation and evaporation upon the occurrence and character of water in streams, lakes, and on or below the land surface. In terms of the hydrologic cycle, the ...

A coating of ice, generally clear and smooth. formed by the freezing of supercooled water on a surface.

Name applied to a class of instruments which measure the liquid content of the atmosphere.

An instrument designed to record the duration of sunshine at a given location without regard to intensity. See Campbell- Stokes recorder, Jordan sunshine recorder, Marvin sunshine recorder, Pers sunshine recorder.

General name for a type of instrument which measures the inclination of the wind to the horizontal plane. See bivane.

Generally, the relative states of inflow, outflow, and storage of moisture over a given area of earth's surface.

A hygrometer which includes an arrangement for the time recording of atmospheric humidity.

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