An instrument which measures the transmissivity of the atmosphere between two points for the determination of visual range.

An instrument used to measure changes in the level of the water in an evaporation pan. The gauge is normally placed in a Stillwell and adjusted so that the point of the hook just breaks the water surface. The change in water level is read on the attached ...

A hydrometeor consisting of a visible aggregate of minute water droplets suspended in the atmosphere near the earth's surface. Fog differs from cloud only in that the base of fog is at the earth's surface while clouds are above the surface.

Of or pertaining to the air, atmosphere, or aviation. Also, same as antenna.

The total electromagnetic radiation emitted by the sun. About 99.9 percent of its energy output falls within the wavelength interval from 0. 15 microns to 4.0 microns, with peak intensity near 0.47 microns. About one-half of the total energy in the solar ...

A clockwise change in wind direction. Veering winds with height are indicative of warm air advection (WAA).

The envelope of air surrounding the earth and bound to it more or less permanently by virtue of the earth's gravitational attraction. The system whose chemical Properties. dynamic motions, and physical processes constitute the subject matter of meteorolog ...

A method of winds aloft observation essentially the same as a pilot balloon observation except the height data is derived from the radiosonde observation rather than from assumed ascension rates.

In a system of moist air, the dimensionless ratio of the mass of water vapor to the total mass of the system.

See gain.

A relatively small-scale, upward moving current of air.

February 2nd. In American folklore, a day that is popularly supposed to provide the key to the weather for the remainder of the winter. Specifically, if the ground-hog upon emerging from its hole casts a shadow, it will return underground, thereby forebod ...

A high-altitude sounding system consisting of a small solid- propellant research rocket carried aloft by a large plastic balloon. The rocket is fired near the maximum altitude of the balloon flight.

A device used to hold liquid-in-glass maximum and minimum thermometers in the proper recording position inside an instrument shelter, and to permit them to be read and reset. See Townsend support.

Same as instrument shelter.

An anemometer in which the sensor rotation is transmitted to a mechanical counter which directly integrates the air movement past the sensor. Used to determine total air passage (wind run). Average wind speed can be calculated from the difference between ...

A rocket designed primarily for routine upper air observations in the lower 250,000 feet of the atmosphere, especially that portion inaccessible to balloons (above 100,000 feet).

A hygrometer in which the rotation of the hygrometric element is a function of humidity.

An instrument which records the duration of sunshine and gives a quantitative measure of the amount of sunshine by the action of the sun's rays upon blueprint paper. A type of sunshine recorder.

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 ...