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

A measure of luminous flux remaining in a light beam after it has passed through a specified distance of the atmosphere.

The stage, on a fixed river gauge, corresponding to the top of the lowest banks within the reach for which the gauge is used as an index. Compare to flood stage.

An addition to a rawinsonde system which allows determination of the slant range to the radiosonde.

A set of regulations set down by the U.S. Civil Aeronautics Board to govern the operational control of aircraft on instrument flight. The abbreviation of this term is seldom used to denote the rules themselves, but is in popular use to describe the weathe ...

A balloon having a detachable tail which is released when the balloon has undergone a predetermined expansion. It thus serves to measure approximately the density of the atmosphere at the point of release.

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

A rocket designed primarily for routine upper air observations in the lower 250,000 feet of the atmosphere, especially that portion inaccessible to balloons (above 100,000 feet).

Readily taking up and retaining moisture.

In thermodynamics, the integrating factor of the differential equation referred to as the first law of thermodynamics, In statistical mechanics, a measure of translational molecular kinetic energy (with three degrees of freedom). In general, the degree of ...

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

Turbulence encountered by aircraft when flying through air space devoid of clouds. Thermals and wind shear are the main causes.

In general, the transformation of data from a "raw" form to some useable form. In meteorology, this often refers to the conversion of the observed value of an element to the value which it would theoretically have at some selected or standard level. The m ...

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.

National Centers for Environmental Prediction. Central computer and communications facility of the National Weather Service; located in Washington, DC.

Radiation with wavelengths less than 4 microns.

Wind with a speed below 1 knot (1 mph); Beaufort scale number 0.

A photoelectric spectrophotometer which is used in the determination of the ozone content of the atmosphere.

General name for an instrument designed to measure the vertical component of the wind speed. See anemoclinometer.

A buoyant balloon kept from rising freely by means of a line secured to a point on the ground, as opposed to a free balloon. See kytoon.