降雨过程中稳定同位素组成分析

Stable Isotope Composition Analysis in Precipitation

降雨过程中凝结和蒸发都会引起降水同位素组成变化。在介绍开放水体凝结过程中的瑞利分馏模型的基础上,对云体作了一定简化和假设。基于瑞利分馏原理和质量守恒定律分别推导了降雨过程中的稳定同位素组成随时间变化和质量变化的微分方程模型,并通过数学推理论证了上述各模型之间的内在联系,导出了降雨过程中稳定同位素组成与分馏系数、时间以及质量之间的定量关系,揭示降雨过程中的同位素比率变化,为数值模拟降雨过程的稳定同位素组成提供了确定性的数学基础,为降雨同位素的纬度效应、高度效应、降雨量效应以及大陆效应解释提供了理论依据。

Stable isotope composition of rainout will be changed in precipitation because of concreting and evaporation. Rayleigh--Model of concreting is introduced in open water body. After making some simplifications and assumptions, the paper gives the differential equation model of stable isotope composition that varies with time and mass of precipitation based on basic law of conservation of mass and Rayleigh fractionation principle. And the models describe the quantitative relations among the fractionation factor, time and mass. Then the inner link among the above models which present the isotopic rate change of precipitation are presented by mathematical deduction. These models＇ proposing makes it possible to simulate the precipitation stable isotope composition quantitatively and gives a theory base to interpret that latitude effect, altitude effect and rainfall effect included stable isotope in precipitation.