An instrument which measures the scattering function of particles suspended in a medium in order to determine the visual range through the medium. See visibility meter.

Meteorological information issued by a watch office concerning the occurrence or forecast of weather phenomena which may affect the safety of aircraft operations.

The height ascribed to the lowest layer of clouds or obscuring phenomena when it is reported as broken, overcast, or obscuration and not classified as "thin" or "partial." The ceiling is termed unlimited when these conditions are not satisfied. ...

A rotation anemometer which has a horizontal axis upon which helicoidal shaped vanes are mounted. See windmill anemometer.

A system of physical units based upon the use of the meter, the metric ton (106 grams), and the second as elementary quantities of length, mass, and time, respectively.

The lowest value of a measured quality at which a sensor meets its accuracy specification.

Same as evaporative power.

See instrument error, observational error. random error, standard error, systematic error.

A thermometer with a muslin-covered bulb which is moistened. used to measure wet-bulb temperature.

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

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 ...

An instrument that shows changes in humidity.

General term for an instrument which records the vertical electric current in the atmosphere.

Rate of flow of water past a point in a stream, expressed as volume per unit time, i.e. cubic feet per second.

See radiosonde commutator.

The range through which the input may be varied without initiating a response. Usually expressed as a percentage of full-scale range.

An instrument for determining the degree of polarization of light. See photopolarimeter.

A device which automatically records the water equivalent of snow on a given surface as a function of time. A small sample of a radioactive salt is placed in the ground in a shielded collimator which directs a beam of radioactive particles upwards. A Geig ...

The downward flux of atmospheric radiation passing through a given level surface, usually taken as the earth's surface. This result of infrared (long-wave) absorption and reemission by the atmosphere is the principal factor in the greenhouse effect.

Same as instrument shelter.