Determined by weighing a special type of wooden stick that has been exposed in the woods, its weight being proportional to its contained water.

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 ...

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

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

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

Of or pertaining to rain.

The portion of the precipitation on the land which ultimately reaches the streams. especially the water from rain or melted snow that flows over the surface.

An instrument for measuring angles of inclination. Used in conjunction with a ceiling light to measure cloud height at night.

Contraction for pilot balloon observation.

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

An instrument for measuring the extinction coefficient in water.

Force wind-Wind with a speed above 64 knots (73 mph); Beaufort scale numbers 12 through 17.

See bimetallic thermometer.

General name for an instrument which measures the evaporation rate of water into the atmosphere. See clay atmometer, evaporation pan, evapotranspirometer, Livingston sphere, Piche evaporimeter, radio atmometer.

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

An accumulation of granular ice tufts on the windward sides of exposed objects that is formed from supercooled fog or cloud and built out directly against the wind.

See captive balloon, ceiling balloon, constant-level balloon, free balloon, hurricane beacon, kytoon, Moby Dick balloon, pilot balloon, radiosonde balloon, rockoon, skyhook balloon, transosonde.

The distance or length of flow of the air past a point during a given interval of time.

A rain gauge which is placed under trees or foliage to determine the rainfall in that location. By comparing this catch with that from a rain gauge set in the open. the amount of rainfall which has been intercepted by foliage can be determined.

An instrument which measures the intensity of radiation by determining the amount of chemical change( or fluorescence produced by that radiation.