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

The maximum difference in output for any given input (within the specified range) when the value is approached first with increasing, and then with decreasing, input signals. Caused by energy absorption in the elements of the measuring instrument. Usually ...

A sunshine recorder of the type in which the time scale is supplied by the motion of the sun. It consists of two opaque metal semi-cylinders mounted with their curved surfaces facing each other. Each of the semi-cylinders has a short narrow slit in its fl ...

The wind speed and direction at various levels in the atmosphere above the level reached by surface weather observations.

Name sometimes given to a transmissometer.

The greatest distance at which it is just possible to see and recognize with the unaided eye (1) in the daytime, a prominent dark object against the sky at the horizon, and (2) at night, a known, preferably unfocused, moderately intense light source.

Solar radiation scattered by particles in the atmosphere.

Same as photometer.

A instrument designed to study small fluctuations of some quantity. The microbarograph is an example of a recording pressure variometer.

An instrument which determines the black-body temperature of a substance by measuring its thermal radiation.

Wind with a speed between 41 and 47 knots (47 and 54 mph); Beaufort scale number 9.

An approximation to the complete equations describing atmospheric motion in which only the terms most important for the growth and decay of synoptic scale extratropical weather systems (i.e., the large areas of high and low pressure seen on weather maps) ...

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

An instrument which measures the spectral distribution of the intensity of direct solar radiation.

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.

General name for a type of instrument which measures the inclination of the wind to the horizontal plane. See bivane.

A reflecting type telescope with a 45

Operation mode of a communication circuit in which each end can transmit and receive, but not simultaneously.

Abbreviation for Instrument Flight Rules, but commonly used to refer to the weather and/or flight conditions to which these rules apply, i.e. low visibility.

A type of cyanometer. an instrument used to measure the blueness of the sky. The Linke-scale is simply a set of eight cards of different standardized shades of blue. They are evenly numbered 2 to 26. The odd numbers are used by the observer if he or she j ...