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

The range of operating conditions within which a device is designed to operate and for which operating influences are stated. See operating conditions, reference operating conditions.

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

A method of upper air observation consisting of an evaluation of the wind speed and direction, temperature, pressure, and humidity aloft by means of a balloon-borne radiosonde tracked by radar or a radio theodolite.

A method of winds aloft observation accomplished by tracking a balloon-borne radar target or radiosonde with either radar or a radio theodolite.

An increase in the central pressure of a pressure system; opposite of a deepening. More commonly applied to a low rather than a high.

The part of a measuring instrument which responds directly to changes in the environment.

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 wind blowing in a direction perpendicular to the course of a moving object.

See evaporative opportunity.

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

A pressure-plate anemometer consisting of a plate which is free to swing about a horizontal axis in its own plane above its center of gravity. The angular deflection of the plate is a function of the wind speed. This instrument is not used for station mea ...

A radiosonde whose carrier wave is modulated by audio-frequency signals whose frequency is controlled by the sensing elements of the instrument.

A graphical device used for the determination of the speed of the geostrophic wind from the isobar or contour-line spacing on a synoptic chart.

In thermodynamics, the integrating factor of the differential equation referred to as the first law of thermodynamics, In statistical mechanics, a measure of translational molecular kinetic energy (with three degrees of freedom). In general, the degree of ...

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 ...

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

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

The difference between temperature measurements taken at two significant levels above the ground. Temperatures at 10 and 40 meters are commonly used.

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