An instrument for measuring radiant energy. See actinometer, Dines radiometer, photometer, Tulipian radiometer.

A hypothetical, ideal body which absorbs completely all incident radiation. independent of wavelength and direction. No actual substance behaves as a true black body, although platinum black and other soots rather closely approximate this ideal. However, ...

Wind with a speed between 56 and 63 knots (64 and 72 mph); Beaufort scale number 11.

A common unit used in measurement of atmospheric pressure. Defined as that pressure exerted by a one-inch column of mercury at standard gravity and a temperature of 0'C.

See hurricane beacon.

See sea-water thermometer, reversing thermometer.

Same as mirror nephoscope.

A unit of luminous flux. The lumen is equal to the luminous flux radiated into a unit solid angle (steradian) from a small source having a luminous intensity of one candle. An ideal source possessing an intensity of one candle in every direction would rad ...

The process by which small particles suspended in a medium of a different refractive index diffuse a portion of the incident radiation in all directions. In scattering no energy transformation results, only a change in the spatial distribution of the radi ...

Meteorological information issued by a watch office concerning the occurrence or forecast of weather phenomena which may affect the safety of aircraft operations.

A cone-tipped metal rod designed to be driven downward into deposited snow or firn. The measured amount of force required to drive the rod a given distance is an indication of the physical properties of the snow or firn.

See mote.

Same as rain gauge.

A device, similar to a potometer, for measuring transpiration, consisting of a vessel containing soil in which one or more plants are rooted and sealed so that water can escape only by transpiration from the plant.

A type of electrical thermometer in which the thermal element is a substance whose electrical resistance varies with the temperature. Such thermometers can be made with very short time constants and are capable of highly accurate measurements.

Wind with a speed between 22 and 27 knots (25 and 31 mph); Beaufort scale number 6.

An atmospheric sounding instrument which is supported by a captive balloon and used to obtain temperature and humidity data from the ground level to a height of a few thousand feet. The data is telemetered to the ground through a wire cable.

A wind blowing in the same direction as the heading of a moving object. thus assisting the object's intended progress. The opposite of a head wind.

Any source of radiant energy, especially electromagnetic energy.

In a system of moist air, the ratio of the mass of water vapor to the total volume of the system. Usually expressed as grams per cubic meter (g/m3).