A buoyant balloon kept from rising freely by means of a line secured to a point on the ground, as opposed to a free balloon. See kytoon.

Video Display Terminal. An input and display device which includes a keyboard and a screen and allows a human to communicate with a computer.

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

See evaporative opportunity.

Any quantity, such as force velocity, or acceleration, which has both magnitude and direction at each point in space, as opposed to scalar which has magnitude only. Such a quantity may be represented geometrically by an arrow of length proportional to its ...

A hygrometer which uses a transducing element whose electrical properties are a function of atmospheric water vapor content. The humidity strip and carbon-film hygrometer element are examples of such a transducer.

See evaporation pan.

An absolute pyhrliometer, developed by C.G. Abbott, in which the radiation-sensing element is a blackened water-calorimeter.

A general term for instruments designed to measure the amount of cloudiness.

Temperature of equilibrium between the liquid and vapor phases of a substance at a given pressure.

Any one of numerous devices for the measurement of either speed alone or of both direction and speed (set and drift) in flowing water.

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

Situated on the side from which the wind blows.

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

A combination cup anemometer and pressure-plate anemometer, consisting of an array of cups about a vertical axis of rotation, the free rotation of which is restricted by a suitable spring arrangement.

A unit measure of electrical conduction. The facility with which a substance conducts electricity, as represented by the current density per unit electrical-potential gradient in the direction of flow. Electrical conductivity is the reciprocal of electric ...

The true freezing point of water. The temperature at which a mixture of air-saturated pure water and pure ice may exist in equilibrium at a pressure of one standard atmosphere.

The maximum distance along the runway at which the runway lights are visible to a pilot at touchdown. Runway visual range may be determined by an observer located at the end of the runway, facing in the direction of landing, or by means of a transmissomet ...

A measure of the attenuation due to scattering, of light as it traverses a medium containing scattering particles.

The decrease of an atmospheric variable with height, the variable being temperature, unless otherwise specified.