The amount of precipitation falling in one day, or other specified period, that is likely to be equalled or exceeded in any given place only once in a century. That is, a precipitation amount that has a return period of 100 years.

Same as recording rain gauge.

Same as rain gauge.

Apparatus from which the nature and time of precipitation may be determined.

An instrument for determining the degree of polarization of light. See photopolarimeter.

An instrument for studying, or examining substances in, polarized light. See Savant polariscope.

Same as evaporative power.

The amount of moisture which, if available, would be removed from a given land area by evapotranspiration. Expressed in units of water depth.

Temperature assumed by an unsaturated air parcel when brought adiabatically to a standard pressure (1,000 mb).

An instrument for measuring differences in electric potential.

A device, similar to a phytometer, for measuring transpiration. It consists of a small vessel containing water and sealed so that the only escape of moisture is by transpiration from a leaf, twig, or small plant with its cut end inserted in the water.

Amount of water, expressed as a depth or as a mass, which would be obtained if all the water vapor in a specified column of the atmosphere were condensed and precipitated.

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

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

For a given location, a measure of the long-range effectiveness of precipitation in promoting plant growth. Also called precipitation-evaporation index.

Same as precipitation-evaporation ratio.

Same as precipitation- effectiveness index.

A measure of long-term precipitation effectiveness. The ratio of the normal annual rainfall to the normal annual evaporation.

For a given locality and month, an empirical expression devised for the purpose of classifying climates numerically on the basis of precipitation and evaporation.

An aneroid barometer with a scale graduated in altitude instead of pressure units.