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, instrument that measures the rate of evaporation of water into the atmosphere, sometimes called an atmometer. Evaporimeters are of two types, those that measure the evaporation rate from a free water surface and those that measure it from a continuously wet porous
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(in meteorology), an instrument for measuring evaporation from the surface of bodies of water and from the soil.
A floating atmometer of the GGI-3000 system (developed by the State Hydrological Institute) is used to measure evaporation from bodies of water in the USSR. It is a cylindrical metal vessel with a conical bottom filled with water; the area of the evaporating surface is 3,000 sq cm. During observation a volumetric burette is placed on a tube attached to the center of the vessel. The burette has an opening at the bottom, into which the water passes. The quantity of water evaporated is determined from the difference in the volumes of water taken up by the burette at two successive time intervals. Atmometers are used in the open sea to estimate the extent of evaporation from changes in the concentration of salts in sea water or from differences in its temperature (Shuleikin’s atmometer).
The GGI-500 atmometer is very widely used to measure evaporation from the soil. It consists of two cylindrical vessels, one inside the other, and a water-collecting vessel. The bottom of the inner cylinder has openings; the core sample is placed in it. The quantity of water evaporated is determined from the difference in weight of the sample as measured over two successive observation periods. Evaporating basins set into the ground, with an area of 20 sq m or more, are used to minimize the effect of the walls and bottom on the measurements.
REFERENCESSternzat, M. S. Meteorologicheskie pribory i nabliudeniia.Leningrad, 1968.
Kedrolivanskii, V. N., and M. S. Sternzat. Meteorologicheskie pribory.Leningrad, 1953.
S. I. NEPOMNIASHCHII