A buoyant balloon rising freely in the atmosphere, as opposed to a captive balloon.

An instrument for measuring the ultraviolet in solar and sky radiation.

Quantitative Precipitation Forecast.

Electromagnetic radiation of very short wavelength. lying within the wavelength interval of 0.1 to 1.5 angstroms (between gamma rays and ultraviolet radiation). X-rays penetrate various thicknesses of all solids, and they act on photographic plates in the ...

Conditions to which a device is subjected, not including the variable measured by the device. See normal operating conditions, reference operating conditions.

Wind with a speed between 28 and 33 knots (32 and 38 mph); Beaufort scale number 7.

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

Of or pertaining to the air, atmosphere, or aviation. Also, same as antenna.

The interval between the lower and upper measuring limits of an instrument, i.e. a thermometer with a range of -35 to 50

Same as precipitation- effectiveness index.

Same as constant-level balloon.

Name sometimes used in place of pyranometer as a generic term.

See evaporative opportunity.

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

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

A clay atmometer consisting of a hollow ceramic sphere through which evaporation occurs. Evaporation is measured by the loss of water from the reservoir which feeds the sphere.

A unit of energy defined as the heat required to raise the temperature of one pound of water one degree Fahrenheit. It is equal to 252.1 calories or to 1055 joules.

Abbreviation for Instrument Flight Rules, but commonly used to refer to the weather and/or flight conditions to which these rules apply, i.e. low visibility.

The mass density of a parcel of air expressed in units of mass per volume.

In folklore, a name for wind.