CAJ | 학술논문

介绍的数学模型考虑了混合云中液、固态共存时以及冰面过饱和环境下稳定同位素的动力分馏效应.利用该数学模型,模拟了不同冷却条件下稳定同位素的温度效应.在相同的湿度条件下,湿绝热冷却过程中δ18O随温度的变化率小于等压冷却过程.冰面过饱和比Si的增大意味着动力分馏效应的增大.与平衡态相比,它的作用使得稳定同位素的综合分馏系数减小,从而使得降水中δ18O随温度的变化趋缓.模拟显示,湿绝热冷却过程中大气水线(MWL:=bδ18O+d)的斜率b和常数d均大于等压冷却过程.全球大气水线位于湿绝热冷却过程和等压冷却过程条件下分别模拟的两条大气水线之间.b和d的大小与Si呈正比.Si愈大,动力分馏效应愈强,b和d也愈大.反之亦然.然而,b和d的大小对云中含水量的变化具有低的敏感性.利用动力分馏模式模拟了乌鲁木齐降水中稳定同位素的变化.模拟的稳定同位素比率-温度以及δD-δ18O曲线分别与乌鲁木齐实测的稳定同位素比率-温度回归线以及大气水线有非常好的一致性.
개소적수학모형고필료혼합운중액、고태공존시이급빙면과포화배경하은정동위소적동력분류효응.이용해수학모형,모의료불동냉각조건하은정동위소적온도효응.재상동적습도조건하,습절열냉각과정중δ18O수온도적변화솔소우등압냉각과정.빙면과포화비Si적증대의미착동력분류효응적증대.여평형태상비,타적작용사득은정동위소적종합분류계수감소,종이사득강수중δ18O수온도적변화추완.모의현시,습절열냉각과정중대기수선(MWL:=bδ18O+d)적사솔b화상수d균대우등압냉각과정.전구대기수선위우습절열냉각과정화등압냉각과정조건하분별모의적량조대기수선지간.b화d적대소여Si정정비.Si유대,동력분류효응유강,b화d야유대.반지역연.연이,b화d적대소대운중함수량적변화구유저적민감성.이용동력분류모식모의료오로목제강수중은정동위소적변화.모의적은정동위소비솔-온도이급δD-δ18O곡선분별여오로목제실측적은정동위소비솔-온도회귀선이급대기수선유비상호적일치성.
The introduced mathematical model takes into account the role of the kinetic fractionation effect in a supersaturation environment at the ice surface as liquid and solid phases coexist in mixed cloud. Using the model, the temperature effect of stable isotopes in precipitation is simulated under different cooling conditions. The rate of change of δ18O against temperature in the process of wet adiabatic cooling is smaller than in the process of isobaric cooling under the same humidity. The increasing supersaturation ratio at the ice surface, Si, leads to the strengthening of the kinetic fractionation effect. The kinetic fractionation function makes the synthesis fractionation factor decreased and the change of δ18O with temperature flatted, compared with that in the equilibrium state. The simulated results show that the slope parameter b and the intercept d of the meteoric water line (MWL), δD = bδ18O+d, in wet adiabatic cooling are both greater than those in isobaric cooling. The global MWL lies between the two MWLs simulated under wet adiabatic and isobaric cooling processes, respectively. The magnitudes of b and d are directly proportional to Si. The greater the Si, the stronger the kinetic fractionation effect, and thus the greater the b and d, and vice versa. However, b and d have low sensitivity to the liquid-water contents in the cloud. Using the kinetic fractionation model, the variation of stable isotopes in precipitation at Urumqi is simulated. The simulated stable isotopic ratio vs temperature and the δD vs δ18O curves are very consistent with the actual regressions and MWL at Uruimqi, respectively.