章新平,谢自楚,姚檀栋. 1998. 降落雨滴中稳定同位素比率变化的数学模拟[J]. 气象学报, 56(1):87-95, doi:10.11676/qxxb1998.008
降落雨滴中稳定同位素比率变化的数学模拟
MATHEMATICAL MODELING OF VARIATION ON STABLE LSOTOPES IN FALLING DROP
投稿时间:1996-05-17  修订日期:1996-11-10
DOI:10.11676/qxxb1998.008
中文关键词:  稳定同位素  雨滴  模式  蒸发
英文关键词:Stable isotope  Water drop  Model  Evaporation
基金项目:国家自然科学基金
作者单位
章新平 湖南师范大学资源与环境学系, 长沙, 410081 
谢自楚 湖南师范大学资源与环境学系, 长沙, 410081 
姚檀栋 中国科学院兰州冰川冻土研究所, 兰州, 730000 
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中文摘要:
      根据扩散定律和热量平衡理论,运用云物理学模式,对降落雨滴中稳定同位素比率的变化进行了数值模拟,发现降落雨滴中稳定同位素比率的变化除受湿度条件的影响外,还受大气水汽中稳定同位素比率的影响。在非饱和大气中,受蒸发过程的影响,降落雨滴中稳定同位素比率随降落距离而不断增大,空气湿度越小,增大幅度越明显。平均而言,大气湿度与dδD/dδ18O和Ex d呈正比。dδD/dδ18O以8为渐近线,Ex d则在高湿和较大半径条件下逐渐趋近于一个常数;在饱和大气中,半径较小的雨滴或在湿度较高的环境中,雨滴中稳定同位素达到平衡的时间较短。反之,达到平衡的时间较长。
英文摘要:
      A ccording to the cloud physics model,the paperanalyses the variations of stable isotopes in raindrops under different conditions,inquires into the im pacts ofenrichment produced due to the evaporation of raindrops below cloud base and the exchange between stable isotopes of the raindrops and surrounding vaporon stable isotopic ratios in the raindrops.Foradrop: (1) Influenced by evaporation process,stable is otopic ratios in the raindrop increase with the falling distance. The less the humidity in atmosphere,the more obvious the range of increasing;on the other hand,if there is a difference bet ween stable isotopic ratios at the boundary layer of the raindrop and in surrounding vapor,the move of stable isotopic composition from high to low value will be produced.Two factors restrictthe variations of stable isotopic ratios in the drop in common.Their direction may be same,or different.Under the condition of saturation,the impact ofevaporation disappears,and the degrees of stable isotopic ratios in the drop are dependenton the exchange with stable isotopic composition in surrounding vapor.If the two processes all keep the equilibrium,namelys=100%,and Rv=Rl/α,then dRl=0,which shows that stable isotopic ratios don't change with the falling distance. (2) Generally,the atmospheric humidityis in direct proportion to dδD/dδ18O and Ex d.In any case,all dδD/dδ18O have a gradual value of equaling 8,and Ex d gradually tends to a constantunder the conditions of the high temperature and the large radii, which might be related to the appearance of "pseudo-equilibrium state". (3) In saturated at mosphere,the time of reaching isotopic equilibriumis short for small drop orin an environment with the high temperature;on the contrary,the time is long.
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