An absolute pyhrliometer, developed by C.G. Abbott, in which the radiation-sensing element is a blackened water-calorimeter.

A coating of ice, generally clear and smooth. formed by the freezing of supercooled water on a surface.

Companion to the wet-bulb thermometer in a psychrometer. Used to measure ambient air temperature.

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

Water vapor content of the air. See absolute humidity, dew point, mixing ratio, relative humidity, specific humidity.

Root Mean Square. This notation is used frequently with error analysis. In that context, it is the square root of the arithmetic mean of the squares of the deviations of the individual calibration points from the theoretical or ideal response.

A device for measuring the height of tide. It may be simply a graduated staff in a sheltered location where visual observations can be made, or it may consist of an elaborate recording instrument (sometimes called a marigraph) making a continuous graphic ...

Wind with a speed between 28 and 55 knots (32 and 63 mph); Beaufort scale numbers 7 through 10.

Tables prepared from the psychrometric formula and used to obtain vapor pressure, relative humidity, and dew point from values of wet-bulb and dry-bulb temperatures.

An instrument used for measuring the specific gravity of a liquid.

A rainbow formed by light rays which have been reflected from an extended water surface. Not to be confused with a reflected rainbow whose image may be seen in a still body of water. The center of a reflection rainbow is at the same elevation as the sun b ...

A set of weekly colored rainbow arcs sometimes discernable inside a primary rainbow.

Routine broadcast of meteorological information for aircraft in flight.

The source of illumination for an antenna reflector. Also called antenna feed.

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

Generally, an instrument designed to measure or estimate the blueness of the sky. See Linke-scale.

A small balloon, loaded with ballast and inflated so that it will explode at a predetermined altitude, which is attached to a larger balloon.

An optical instrument which consists of a sighting telescope mounted so that it is free to rotate around horizontal and vertical axes, with graduated scales so that the angles of rotation may be measured. Used to observe the motion of a pilot balloon.

A pyrheliometer of the thermoelectric type. Radiation is allowed to fall on two concentric silver rings, the outer covered with magnesium oxide and the inner covered with lamp black. A system of thermocouples (thermopile) is used to measure the temperatur ...

The elevation of the water surface in a stream as measured by a river gauge with reference to some arbitrarily selected zero datum.