A unit of luminance or brightness equal to 1/d candles per foot'.

A polariscope consisting of a specially constructed double plate polarizer and a tourmaline plate analyzer. Polarized light passing through the instrument is indicated by the presence of parallel colored fringes, while unpolarized light results in a unifo ...

An absolute temperature scale with the ice point of pure water defined as 273.16 K. The size of the degree is the same as on the Celsius scale, and the zero point is absolute zero.

pattern barometer-Mercurial barometer with a fixed scale and cistern and which therefore requires only one adjustment before each reading.

The distance or length of flow of the air past a point during a given interval of time.

In a system of moist air, the dimensionless ratio of the mass of water vapor to the total mass of the system.

Same as an upper air observation, but commonly used to refer to a single complete radiosonde observation.

A precipitation gauge consisting of a receiver in the shape of a funnel which empties into a bucket mounted upon a weighing mechanism. The weight of the catch is recorded as inches of precipitation.

A radiosonde which transmits the indication of the meteorological sensing elements in the form of a code consisting of combinations of dots and dashes.

The total luminous flux received on a unit area of a given real or imaginary surface, expressed in such units as the foot-candle, lux, or phot.

The temperature at which an object gives out as much radiation as it receives from its surroundings.

A numbering system using a base number of 2 and having only two digits: 0 and 1. The fundamental system of representing information with electrical pulses.

In a system of moist air, the dimensionless ratio of the mass of water vapor to the mass of dry air. For many purposes, the mixing ratio may be approximated by the specific humidity.

An atmometer which uses a filter paper disc as the evaporating element. The amount of water evaporated through the paper is read at the graduated tube reservoir.

A small anemometer with flat vanes which indicates the number of linear feet or meters of air which have passed the instrument during its exposure.

Routine broadcast of meteorological information for aircraft in flight.

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 radiosonde equipped to measure temperature only.

A local variation of the wind vector or any of its components in a given direction.

An Instrument used to determine dew point.