An evaluation, according to set procedures, of those weather elements which are most important for aircraft operations. Always includes cloud height or vertical visibility, sky cover, visibility, obstructions to vision, certain atmospheric phenomena, and ...

The unit of acceleration in the centimeter-gram-second system of units, equal to one cm per sec2. Commonly used in gravimetry.

A photoelectric spectrophotometer which is used in the determination of the ozone content of the atmosphere.

A type of photoelectric photometer used to measure high-altitude winds on the assumption that stellar scintillation is caused by atmospheric inhomogeneities being carried along by wind near the tropopause level.

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 device for measuring the frequency of occurrence of atmospherics whose intensity is greater than a predetermined level.

The lowest value of a measured quality at which a sensor meets its accuracy specification.

Of or pertaining to rain.

The difference between amounts of precipitation and runoff for a given storm. It is that portion of the precipitation that remains in the basin as soil moisture, surface storage, ground water, etc.

A conductor or system of conductors for radiating and/or receiving radio energy. Also called aerial.

Instrument for measuring the mean intensity of glo global solar radiation (direct and diffuse) near the earth's surface in a specified time interval.

The processing of the form or mode of a signal so as to make it intelligible to, or compatible with, a given device.

Upwarddirected solar radiation, reflected by the earth's surface and the atmosphere.

A device for measuring the river stage. Also called stream gauge.

The value of the quantity measured, as indicated or otherwise provided by a measuring instrument.

Same as mercury barometer.

A clock-driven instrument mounting which automatically and continuously points in the direction of the sun. It is used with a pyrheliometera,hen continuous direct solar radiation measurements are required.

Board that holds graph paper on which is plotted information obtained from a pilot-balloon observation.

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

An instrument used to measure the water vapor content of the air.