See bimetallic thermometer.

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

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

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

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

Radio Direction Finder.

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

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.

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

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

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

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

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.

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

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

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.

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

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

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

Literally "not wet", containing no liquid.