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 ...

A radiosonde which transmits the indication of the meteorological sensing elements in the form of a code consisting of combinations of dots and dashes.

A device which converts energy from one form into another, i.e. an ac generator transducer which converts the mechanical motion of anemometer cups into an electrical signal.

An anemometer which measures wind speed by means of the properties of wind-borne sound waves. It operates on the principle that the propagation velocity of a sound wave in a moving medium is equal to the velocity of sound with respect to the medium plus t ...

An area of low barometric pressure, with its attendant system of winds. Also called a depression or cyclone.

Reduction of visibility by strong winds blowing across dry ground with little or no vegetation. Visibilities of 1/8 mile or less over a widespread area are criteria for a Blowing Dust Advisory.

An instrument for recording ocean waves. Most recorders are designed for recording wind waves, that is waves of periods up to about 25 seconds, but some are designed to record waves of longer periods such as tsunamis or tides.

A thin metal disc partially evacuated of air used to measure atmospheric pressure by measuring its expansion and contraction.

A component of a radiosonde consisting of a series of alternate electrically conducting and insulating strips. As these are scanned by a contact the radiosonde transmits temperature and humidity signals alternately. The contact may be a baroswitch as in t ...

Either of two colored luminous spots that appear at points 22

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

An aneroid barograph designed to record atmospheric pressure variations of very small magnitude.

A graphical representation of stage or discharge at a point on a stream as a function of time.

Radiation with wavelengths less than 4 microns.

An instrument for recording global solar radiation.

A device used by oceanographers to obtain subsurface samples of sea water. The "bottle" is lowered by wire, its valves open at both ends. It is then closed in situ by allowing a weight (called a messenger) to slide down the wire and strike the reversing m ...

The limiting values of ceiling, visibility, and wind, or runway visual range, established as safety minimum for aircraft landings and take-offs.

A measure, proposed by Angstrom, of the precipitation effectiveness of a region.

A device for measuring the river stage. Also called stream gauge.

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