The visibility along an identified runway, determined from a specified point on the runway with the observer facing in the same direction as a pilot using the runway. Compare to runway visible range.

A definite portion of a stream channel, commonly taken between two gauging stations, but may be taken between any two specified points.

A general term for instruments designed to measure the speed or force of the wind.

See evaporation pan.

Capacity of a soil or other surface to be penetrated by water sinking into the ground under the force of gravity. It thus expresses the rate of percolation.

Anemometer which measures wind speed by measuring the degree of cooling of a metal film heated by an electric current. A type of cooling-power anemometer.

Movernent of water through the soil surface into the soil, or the quantity of water entering the soil. Infiltration is equal to the total precipitation less the losses due to interception by vegetation. retention in depressions on the land surface, evapor ...

A thermometer which utilizes the thermal properties of gas. There are two forms of this instrument: (a) a type in which the gas is kept at constant volume, and pressure is the thermometric property, and (b) a type in which the gas is kept at constant pres ...

General term for any device that measures precipitation: principally a rain gauge or snow gauge.

Same as luminous intensity.

Situated on the side from which the wind blows.

The writing component of a recording instrument.

Same as fogbow.

A device which surrounds a rain gauge and acts to maintain horizontal flow in the vicinity of the funnel so that the catch will not be influenced by eddies generated near the gauge. See Alter shield, Nipher shield, Wild fence.

The rate of decrease of pressure per unit distance at a fixed time.

A rainbow of angular radius of about 50

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

The atmospheric pressure computed using station elevation as the reference datum level. Station pressure is usually the base value from which sea level pressure and altimeter setting are determined.

Programs or instructions which are stored in readonly memory.

An instrument, dropped from high attitude and carried by a stable parachute. used to measure the vertical component of turbulence aloft.