The amount of sky covered or concealed by clouds or obscuring phenomena. It is reported in tenths, so that 0.0 indicates a clear sky and 1.0 (or 10/10) indicates a completely covered sky. The following classifications are used in aviation weather observat ...

A graphical aid used in fire weather forecasting to calculate the degree of forest-fire danger (or burning index). Commonly in the form of a circular slide rule, the firedanger meter relates numerical indices of (a) the seasonal stage of foliage, (b) the ...

A series of Nansen-bottle water samples and associated temperature observations resulting from one release of a messenger.

See captive balloon, ceiling balloon, constant-level balloon, free balloon, hurricane beacon, kytoon, Moby Dick balloon, pilot balloon, radiosonde balloon, rockoon, skyhook balloon, transosonde.

An instrument which measures the effective terrestrial radiation. See Angstrom pyrgeometer.

A special type of radar target, usually a comer reflector, tied beneath a free balloon and designed to be an efficient reflector of radio energy.

A thermometer using transducing elements which deform with temperature. Examples are the bimetallic thermometer and the Bourdon tube type of thennometer.

In folklore, a name for rain.

See constant-level balloon.

The effect upon the measurement of rainfall caused by the presence of the rain gauge.

A type of climatic diagram whose coordinates are some form of temperature vs. a form of humidity or precipitation.

Contraction for radiosonde observation.

Determination of the total amount of snow covering a watershed or a given region. Both depth and water content of the snow may be measured, and the results may be used to predict the amount of water that will be available after melting.

Wind with a speed between 48 and 55 knots (55 and 63 mph), Beaufort scale number 10.

An automatic, recording cloud height indicator.

A device attached to a meteorological instrument to provide ventilation; usually a suction fan.

The atmospheric pressure at the level of the barometer. May or may not be the same as station pressure.

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

An instrument for collecting liquid water from the atmosphere.

In meteorology, an area of low pressure; a low or trough.