The probability distribution of random errors, typically a normal distribution with a zero mean.

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.

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

A weakly colored lunar halo identical in form and optical origin to the solar parhelion.

The lowest level at which the wind becomes geostrophic in the theory of the Ekman spiral. Also called gradient wind level.

Pertaining to the action or effect of the wind. Derived from the name of the Greek god of the winds, Aeolus.

Same as pitot tube.

An absolute instrument developed by K. Angstrom for the measurement of direct solar radiation. The radiation receiver station consists of two identical manganin strips whose temperatures are measured by attached thermocouples. One of the strips is shaded, ...

Electromagnetic radiation of very short wavelength. lying within the wavelength interval of 0.1 to 1.5 angstroms (between gamma rays and ultraviolet radiation). X-rays penetrate various thicknesses of all solids, and they act on photographic plates in the ...

An automatic, recording cloud height indicator.

The frequency of a carrier wave.

A hypothetical temperature characterized by a complete absence of heat and defined as 0 K, -273.15 C, or -459.67 F.

An evaluation of upper air temperature, pressure, and humidity from radio signals received from a balloon- borne radiosonde.

Transistor-Transistor Logic.

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

Same as mirror nephoscope.

A measure of luminous flux remaining in a light beam after it has passed through a specified distance of the atmosphere.

A decrease in the central pressure of a pressure system. Usually applied to a low rather than to a high.

An aviation weather forecast for a specific flight.

Value of soil moisture, expressed as a percentage of the mass of dry soil, below which a plant living in the soil dies by wilting.