A rotation anemometer in which the axis of rotation is horizontal. The instrument has either flat vanes (as in the air meter) or helicoidal vanes (as in the propeller anemometer). The relation between wind speed and angular rotation is almost linear.

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

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

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

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

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

See evaporative opportunity.

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

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

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

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.

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 ...

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

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

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

The unit of force in the centimeter-gram-second system of physical units, i.e. one gm cm per sec2, equal to 7.233 x 10-5 poundal.

Any device or instrument for measuring salinity, especially one based on electrical conductivity methods.