The process in which incident radiation is retained by a substance. A further process always results from absorption.

A general name for instruments which detect the presence of (but do not necessarily measure) small electrical charges by electrostatic means. Compare to electrometer.

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

A hygrometer based upon the diffusion of water vapor through a porous membrane.

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.

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.

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.

A form of data transmission in which the bits of each character are all sent simultaneously, resulting in extremely fast communication but requiring a communication path for each bit. Compare to serial data transmission.

A refraction phenomenon similar to a parahelion, but occurring generally at a distance of 120

A faintly-colored circular arc similar to a rainbow but formed on fog layers containing drops whose diameters are 100 microns or less. Also called mistbow, white rainbow.

The elevation of the water surface in a stream as measured by a river gauge with reference to some arbitrarily selected zero datum.

Solar and terrestrial radiation directed downwards (towards the earth's surface); incoming radiation.

Liquid water at temperatures colder than freezing.

A reflecting type telescope with a 45

Abbreviation for radio frequency.

An instrument for the measurement of the radon content of the atmosphere.

The smallest change in the environment that causes detectable change in the indication of an instrument. Compare to sensitivity.

A thermometer designed for use in measuring the temperature of sea water. One form consists of a mercury-in-glass thermometer protected by a perforated metal case. Another form consists of a mercury-in-glass thermometer surrounded by a metal case which fo ...

A wind blowing in a direction opposite to the heading of a moving object, thus opposing the object's intended progress; the opposite of a tailwind.

Generic term for rapid variations in apparent position, brightness, or color of a distant luminous. object viewed through the atmosphere.