Wind with a speed between 4 and 27 knots (4 and 31 mph); Beaufort scale numbers 2 through 6.

An instrument for measuring the intensity of direct solar radiation at normal incidence. See Angstrom compensation pyrheliometer, Eppley pyrheliometer, Michaelson actinograph. silver- disc pyrheliometer, spectropyrheliometer, waterflow pyrheliometer.

An instrument for photographing the corona and prominences of the sun at times other than at solar eclipse.

The inaccuracy that the manufacturer permits when the unit is calibrated in the factory.

General name for a type of instrument which measures the inclination of the wind to the horizontal plane. See bivane.

Radio Direction Finder.

A device for obtaining a continuous record of stage at a point on a stream. The most common recorders consist of a float-actuated pen which traces a record on a clock driven chart.

Strong winds concentrated within a narrow band in the atmosphere. The jet stream often "steers" surface features such as front and low pressure systems.

The height at which the maximum wind speed occurs, determined in a winds-aloft observation.

An ion counter of the aspiration condenser type, used for the measurement of the concentration and mobility of small ions in the atmosphere.

A unit of energy per unit area commonly employed in radiation theory. Equal to one gram-calorie per square centimeter.

The pressure exerted by the atmosphere as a consequence of gravitational attraction exerted upon the "column" of air lying directly above the point in question.

An instrument which measures evaporation by measuring the loss of water from a burette reservoir through a ceramic disc.

An instrument, located at the surface observing station, which is used to record the data presented by a radiosonde aloft.

A small anemometer with flat vanes which indicates the number of linear feet or meters of air which have passed the instrument during its exposure.

Winds from the four cardinal points of the compass; that is, north, east, south, and west winds.

A clock-driven device for recording the time of occurrence of an event or the time interval between the occurrence of events.

Old snow that has become granular and compacted as a result of melting and refreezing.

A mercury barometer in which the lower mercury surface is larger in area than the upper surface. The basic construction of a cistern barometer is as follows: A glass tube one meter in length, sealed at one end is filled with mercury, and then inverted. Th ...

Very generally, any moving- stream of air. It has no particular technical connotation.