That horizontal wind velocity at which the Coriolis acceleration exactly balances the horizontal pressure force. It is directed along contour lines or isobars.

An approximation to the complete equations describing atmospheric motion in which only the terms most important for the growth and decay of synoptic scale extratropical weather systems (i.e., the large areas of high and low pressure seen on weather maps) ...

Same as pitot tube.

An instrument for rapidly obtaining samples of airborne dust; a type of dust counter. Particles pass through a cylindrical chamber, are drawn at high velocity through a narrow slit, and then impinge upon a microscope cover glass located a short distance f ...

A method of streamflow routing which assumes that storage is a linear function of the weighted flow in the reach and is adaptable to a simple mathematical solution.

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 ...

Same as mercury barometer.

The interval between the lower and upper measuring limits of an instrument, i.e. a thermometer with a range of -35 to 50

Precipitation falling from a cloud, usually in wisps or streaks, but evaporating before it reaches the ground.

A radiosonde whose carrier wave is switched on and off in such a manner that the interval of time between the transmission of signals if a function of the magnitude of the meteorological elements being measured.

A device for measuring sea-surface waves. It consists of a weighted pole below which a disk is suspended at a depth sufficiently deep for the wave motion associated with deepwater waves to be negligible. The pole will then remain nearly as if anchored to ...

The older name for the Celsius temperature scale. Officially abandoned by international agreement in 1948, but still in common use.

Water vapor content of the air. See absolute humidity, dew point, mixing ratio, relative humidity, specific humidity.

A forecast of weather elements of particular interest to aviation; including ceiling, visibility, upper winds, icing, turbulence, precipitation types, and storms.

See hook gauge.

An instrument which determines the black-body temperature of a substance by measuring its thermal radiation.

Situated on the side from which the wind blows.

See gain.

A unit of energy equal to 101 ergs or to 0.2389 calories.

Temperature assumed by an unsaturated air parcel when brought adiabatically to a standard pressure (1,000 mb).