A measure of the attenuation due to scattering, of light as it traverses a medium containing scattering particles.

A unit of power equal to one joule per second or 10' ergs per second.

Ragged low clouds, usually stratus fractus. Most often applied when such clouds are moving rapidly beneath a layer of nimbostratus.

A vector term which includes both wind speed and wind direction.

The direction, with respect to magnetic north, from which the wind is blowing. Distinguish from true wind direction.

An estimate of the temperature of an incandescent body, determined by observing the wavelength at which it is emitting with peak intensity (its color) and using that wavelength in Wien's law.

Electromagnetic radiation lying within the wavelength interval to which the human eye is sensitive, the spectral interval from approximately 0.4 to 0.7 microns (4000 to 7000 angstroms). Bounded on the short-wavelength end by ultraviolet radiation and on t ...

A general name for instruments which detect the presence of (but do not necessarily measure) small electrical charges by electrostatic means. Compare to electrometer.

A photometer that measures the received intensity of a distance tight source.

A unit of energy defined as the heat required to raise the temperature of one pound of water one degree Fahrenheit. It is equal to 252.1 calories or to 1055 joules.

In general, any object that reflects incident energy. Usually it is a device designed for specific reflection characteristics.

Pyrheliometer based on the comparison of the heating of two identical metal strips, one exposed to radiation, the other to a joule effect.

Difference between the temperatures of the dry-bulb and the wet-bulb thermometers of a psychrometer.

A radiosonde whose carrier wave is switched on and off in such a manner that the interval of time between the transmission of signals if a function of the magnitude of the meteorological elements being measured.

A scale with the ice point at zero degrees and the boiling point of water at 80 degrees, with pressure of one atmosphere.

See evaporative opportunity.

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

Name given to the unit of pressure in the International System of Units (SI). Equal to 1 newton/meter2 or 0.01 millibar.

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

The nautical mile is closely related to the geographical mile which is defined as the length of one minute of arc on the earth's equator. By international agreement, the nautical mile is now defined as 1852 meters.