Atmospheric Precipitation
Historical document, translated for reference. It reflects medical knowledge of the 1920s–30s and is not medical advice.
Summary
This article from the 1928–1936 Soviet medical encyclopedia defines atmospheric precipitation as the fall of water vapor condensation products from the atmosphere. It details the various forms of precipitation—dew, rain, snow, frost, and hail—and the diverse physical causes that lead to condensation, including contact with cooled surfaces, evaporation into cooler air, radiation, and adiabatic expansion. The text also describes the formation of raindrops and ice crystals and explains how the quantity of precipitation is measured by the thickness of the water layer it would form.
Encyclopedia article (1928–1936)
Atmospheric Precipitation is the fall of condensation products of water vapor contained in the atmosphere. It can occur in the form of dew, or in the form of rain, or in the form of snow, or of frost, or, finally, in the form of hail. Condensation can occur under the influence of the most diverse causes: from the contact of moist air with the surface of the soil, cooled by nocturnal radiation (dew) or by preceding colds (frost); upon evaporation from a surface having a higher t° into a medium with a lower t°, or upon the mixing of two masses (close to saturation) having different t°; upon the radiation of moist masses to strongly cooled ground or, in general, to a medium with a lower t°. Finally, condensation is possible during simple adiabatic expansion of moist air. The initial sizes of the droplets, from which a cloud gradually grows, fluctuate within the limits from 5·10-5 to 5·10-8 cm. Upon further increase in the size of the droplet, it begins to fall rapidly (it no longer remains in a suspended state). Raindrops are formed by the merging of small droplets; their sizes usually fluctuate within the limits from 0.5 to 5 mm. If moist air is subjected to very strong cooling, then the elements of condensation are represented by ice crystals. During their growth, the formation of snowflakes or hailstones occurs, depending on meteorological conditions. The quantity of atmospheric precipitation is characterized by the thickness of the layer of water which they could form in the absence of runoff and evaporation. The maximum daily quantity of precipitation is observed in India, where it reaches 1,036 mm.
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“Atmospheric Precipitation.” Soviet Medical Encyclopedia. English translation of Bolshaya Meditsinskaya Entsiklopediya, 1st ed. (Moscow, 1928–1936), ed. N. A. Semashko. https://sovietmedicalencyclopedia.pages.dev/article/atmospheric-precipitation/