A colorless and odorless gaseous element. The lightest and apparently the most abundant chemical element in the universe. However, it is found only in trace quantities in the observable portion of our atmosphere, only about 0.00005 percent by volume of dr ...

A type of wind vane having a split or V-shaped tail. The apex orients itself to the direction of the wind.

The record or trace made by a microbarograph.

An instrument for measuring snow hardness in terms of the resistance of snow to the pressure exerted by a disk attached to a spring-loaded rod, a gauge calibrated in pounds per square inch registers the amount of resistance. See Canadian hardness gauge.

An instrument for measuring the ultraviolet in solar and sky radiation.

A mercury barometer of the fixed cistern type in which a moveable scale terminating in an ivory point is used to compensate for the variations in the height of the mercury in the cistern

A unit of distance equal to 5280 feet. It is sometimes referred to as a land mile.

A box-like structure designed to protect certain meteorological instruments from exposure to direct sunlight, precipitation, and condensation, while at the same time providing adequate ventilation. Instrument shelters are painted white, have louvered side ...

A record obtained from a meteorograph. A chart in which meteorological variables are plotted against time.

An area of low barometric pressure, with its attendant system of winds. Also called a depression or cyclone.

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.

The time required for an instrument to registe 63.2% of a step change in the variable being measured.

A hygrometer based upon the diffusion of water vapor through a porous membrane.

A rocket designed primarily for routine upper air observations in the lower 250,000 feet of the atmosphere, especially that portion inaccessible to balloons (above 100,000 feet).

The quantity to be measured (or modulated, or detected, or operated upon) which is received by an instrument. Thus, for a thermometer. temperature is the input quantity.

Thermometer for measuring the temperature in the soil at different depths.

Thermodynamic change of state of a system in which there is transfer of heat across the boundaries of the system. Compare to adiabatic process.

A pyrheliometer of the bimetallic type used to measure the intensity of direct solar radiation.

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 ...

variable audio-modulated radiosonde developed at the Bureau of Standards and used by the United States weather services.