A defective maximum thermometer of the liquid-inglass type in which the mercury flows too freely through the constriction. Such a thermometer will indicate a maximum temperature that is too low.

Same as fogbow.

Precipitation composed of balls or irregular lumps of ice with diameters between 5 and 50 mm.

Readily taking up and retaining moisture.

The element directly responsive to the value of the measured variable.

A photometer that measures the received intensity of a distance tight source.

See calorie.

A set of regulations set down by the U.S. Civil Aeronautics Board to govern the operational control of aircraft on instrument flight. The abbreviation of this term is seldom used to denote the rules themselves, but is in popular use to describe the weathe ...

A rain gauge or array of rain gauges designed to measure the inclination and direction of falling rain.

A severe weather condition characterized by low temperatures and strong winds bearing a great amount of snow, either falling or picked up from the ground.

Operation mode of a communication circuit in which each end can simultaneously transmit and receive.

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

A wind blowing in a direction opposite to the heading of a moving object, thus opposing the object's intended progress; the opposite of a tailwind.

See ceilometer.

See foehn.

In Jeffreys' classification, a wind for which the pressure force exactly balances the viscous force, in which the vertical transfers of momentum predominate.

Wind with a speed between 4 and 6 knots (4 and 7 mph), Beaufort scale number 2.

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

National Weather Service. Administered by the U.S. Department of Commerce.

Particle on which the freezing of water occurs.