MATHEMATICAL MODELING OF VARIATIONS ON STABLE ISOTOPIC RATIOS IN FALLING RAINDROPS

<正> The variations of stable isotopic contents in falling raindrops are not only influenced by thehumidity conditions, but also by the stable isotopic contents in atmospheric vapor to a certainextent. If there is a difference between the isotopic contents in the vapor of the surrounding air andat the surface of the raindrops, the move of the isotopic contents from high to low values will beproduced. Usually. influenced by the evaporation process, the stable isotopic ratios in raindropsare constantly increased in the unsaturated atmosphere. The less the atmospheric humidity, themore obvious the increased range. As the enrichment rate of stable isotopes in raindrops is equal tothe outward isotopic move rate. the "pseudo-equilibrium state" appears. The influence ofevaporation on stable isotopic contents disappears in the saturated atmosphere, so that themagnitude of isotopic ratio in raindrops is dependent on the isotopic exchange between theraindrops and the surrounding atmosphere.