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

A unit of illuminance or illumination equal to one lumen per foot'. This is the illuminance provided by a light source of one candle at a distance of one foot.

The succession of stages through which water passes on the ground and in the atmosphere: evaporation from land or bodies of water, condensation to form clouds, precipitation, accumulation in the soil or in bodies of water, and re-evaporation.

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

A flower-like diagram indicating the relative frequencies of different wind directions for a given station and period of time.

The record obtained from a bolometer.

Hygrometer in which the dew (frost) point is determined by observing the temperature of an artificially cooled surface at the moment at which dew (frost) first appears on it.

A generic term for any machine that enables a human being to communicate with a computer.

Anemometer which generates an electrical contact output with a frequency proportional to wind speed.

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

An increase in the central pressure of a pressure system; opposite of a deepening. More commonly applied to a low rather than a high.

An instrument which measures evaporation by measuring the loss of water from a burette reservoir through a ceramic disc.

An instrument for studying, or examining substances in, polarized light. See Savant polariscope.

The total infrared radiation emitted from the earth's surface. To be carefully distinguished from atmospheric radiation, effective terrestrial radiation, and insolation.

A chronograph used to make a time-record of certain measured meteorological elements. The most common type, the triple register, records wind direction and speed, duration of sunshine, and amount of rainfall (sensed respectively by a contact anemometer, M ...

Readily taking up and retaining moisture.

A transducer for converting thermal energy directly into electrical energy. It is composed of pairs of thermocouples which are connected either in series or in parallel. Thermopiles are used in thermoelectric radiation instruments when the output of a sin ...

Of equal or constant pressure, with respect to either space or time.

A line drawn through all points on a map having the same amount of cloudiness.

An automatic, recording cloud height indicator.