By international agreement, a period during which greatly increased observation of world-wide geophysical phenomena is undertaken through the co-operative effort of participating nations. July 1957-December 1958 was the first such year. However, precedent ...

A record obtained from a meteorograph. A chart in which meteorological variables are plotted against time.

The length of air flow past a wind vane required for the vane to respond to 50 percent of a step change in wind direction. Expressed in feet or meters and calculated from delay time times wind tunnel speed.

Any and all forms of water particles, liquid or solid, that fall from the atmosphere and reach the ground.

A mercury-in-glass thermometer which records the temperature upon being inverted and retains its reading until being returned to the first position.

A polarimeter utilizing a Wollaston prism as a polarizer and a Nicol prism as an analyzer.

The time required for an instrument to registe 63.2% of a step change in the variable being measured.

A line drawn through geographical points having the same duration of sunshine (or other function of solar radiation) during a given interval of time.

A unit of energy equal to 1.356joules.

An air-launched balloon designed to be released in the eye of a tropical cyclone, float within the eye at predetermined levels, and transmit radio signals for RDF positioning.

An instrument used to measure the water vapor content of the air. A type of hygrometer. It consists of a wet-bulb and a dry-bulb thermometer. See aspiration psychrometer, Assmann psychrometer. hygrodeik, sling psychrometer.

Amount of solar radiation incident, per unit area and time, on a surface which is perpendicular to the radiation and is situated at the outer limit of the atmosphere, the earth being at its mean distance from the sun. It equals approximately 2.00 ly/ min ...

A pyrheliometer of the bimetallic type used to measure the intensity of direct solar radiation.

An atmometer which uses a filter paper disc as the evaporating element. The amount of water evaporated through the paper is read at the graduated tube reservoir.

A defective maximum thermometer of the liquid-inglass type in which the mercury flows too freely through the constriction. Such a thermometer will indicate a maximum temperature that is too low.

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

A device for measuring the river stage. Also called stream gauge.

A thermopile used in some types of radiation instruments. See solarimeter.

The total electromagnetic radiation emitted by the sun. About 99.9 percent of its energy output falls within the wavelength interval from 0. 15 microns to 4.0 microns, with peak intensity near 0.47 microns. About one-half of the total energy in the solar ...

A type of electrical thermometer in which the thermal element is a substance whose electrical resistance varies with the temperature. Such thermometers can be made with very short time constants and are capable of highly accurate measurements.