A thermometer whose sensitive element has been made to resemble a black body by covering it with lamp black. The thermometer is placed in an evacuated transparent chamber which is maintained at a constant temperature. The instrument responds to insolation ...

See mote.

A line drawn through points of equal humidity on given surface.

A surface weather observation, made at periodic times, of sky cover, state of the sky, cloud height, atmospheric pressure reduced to sea level, temperature, dew point, wind speed and direction. amount of precipitation, hydrometeors and lithometeors. and s ...

The portion of the strearnflow during any month or year derived from precipitation in previous months or years.

Same as atmometer.

A hygrometer which determines the amount of precipitable moisture in a given region of the atmosphere by measuring attenuation of radiant energy caused by the absorption bands of water vapor.

Same as aneroid barometer. Holostelic means wholly made of solids, while aneroid means devoid of liquid.

An instrument for measuring the intensity of direct solar radiation at normal incidence. See Angstrom compensation pyrheliometer, Eppley pyrheliometer, Michaelson actinograph. silver- disc pyrheliometer, spectropyrheliometer, waterflow pyrheliometer.

See standard atmosphere.

An instrument, located at the surface observing station, which is used to record the data presented by a radiosonde aloft.

A buoyant balloon kept from rising freely by means of a line secured to a point on the ground, as opposed to a free balloon. See kytoon.

A type of cistern barometer in which the level of mercury in the cistern is adjusted to the zero point of the scale before each reading.

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

A forecast of weather elements of particular interest to aviation; including ceiling, visibility, upper winds, icing, turbulence, precipitation types, and storms.

An instrument for measuring the ultraviolet in solar and sky radiation.

An instrument for the measurement of the radon content of the atmosphere.

An instrument consisting of a series of graduated cylinders possessing selective collection efficiencies. It is used for the measurement of quantities relating to the size distribution of cloud droplets.

An instrument that shows changes in humidity.

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