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 ...

General term for any device that measures precipitation: principally a rain gauge or snow gauge.

Name applied to a class of instruments which measure the liquid content of the atmosphere.

Generally, an instrument designed to measure or estimate the blueness of the sky. See Linke-scale.

An inert gas. A colorless, monatomic element which is found to occur in dry air to the extent of only 0.000524 percent by volume. Helium is very light, having a molecular weight of only 4.003 and specific gravity referred to air of 0.138. Because helium i ...

An instrument which automatically records the measurement of two or more meteorological elements.

A temperature telemeter.

A curve showing the variation of temperature with height in the free air. See lapse rate.

A basic equation in daytime visual range theory, relating the apparent luminance of a distant black object, the apparent luminance of the background sky above the horizon, and the extinction coefficient of the atmosphere, or the air layer near the ground. ...

A wind (or component thereof) directed down the slope of an incline and caused by greater air density near the slope than at the same levels some distance horizontally from the slope. Also called drainage wind and sometimes called katabatic wind.

A type of hygrometer which measures the water vapor content of the atmosphere by means of the absorption of vapor by a hygroscopic chemical.

Name sometimes given to a transmissometer.

See sea-water thermometer, reversing thermometer.

A colorless and odorless gaseous element. The lightest and apparently the most abundant chemical element in the universe. However, it is found only in trace quantities in the observable portion of our atmosphere, only about 0.00005 percent by volume of dr ...

A radiosonde whose carrier wave is switched on and off in such a manner that the interval of time between the transmission of signals if a function of the magnitude of the meteorological elements being measured.

A cylinder installed in a body of water or an evaporation pan to hold a sensor, such as a float to measure water level or a hook gage. The stillwell is constructed so that there is free movement of water in and out of it, and it therefore provides a repre ...

The scientific study of the waters of the earth, especially with relation to the effects of precipitation and evaporation upon the occurrence and character of water in streams, lakes, and on or below the land surface. In terms of the hydrologic cycle, the ...

See radiosonde commutator.

See radar theodolite, radio direction-finder.

The record or trace made by a microbarograph.