| Simulations of Stable Isotopic Fractionation in Mixed Cloud in Middle Latitudes―Taking the Precipitation at ürǖmqi as an Example |
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| 作者姓名： | ZHANG Xinping YAO Tandong LIU Jingmiao TIAN Lide Masayoshi NAKAWO |
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| 作者单位： | [1]ResearchInstituteforHumanityandNature,Kyoto602-0878,Japan [2]CollegeofResourcesandEnvironmentSciences,HunanNormalUniversity,Changsha410081 [3]LaboratoryofIceandColdRegionsEnvironment,ColdandAridRegionsEnvironmentalandEngineeringResearchInstitute,ChineseAcademyofSciences,Lanzhou730000 [4]ChineseAcademyofMeteorologicalSciences,Beijing100081 |
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| 摘 要： | 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.
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| 关 键 词： | 中纬度地区 混合云 稳定同位素 数学模型 乌鲁木齐市 降水 动力分馏效应 湿度条件 |
| 收稿时间： | 26 February 2002 |
Simulations of stable isotopic fractionation in mixed cloud in middle latitudes-Taking the precipitation at Ürümqi as an example |
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| ZHANG Xinping,YAO Tandong,LIU Jingmiao,TIAN Lide,Masayoshi NAKAWO.Simulations of stable isotopic fractionation in mixed cloud in middle latitudes-Taking the precipitation at ürümqi as an example[J].Advances in Atmospheric Sciences,2003,20(2):261-268. |
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| Authors: | Zhang Xinping Yao Tandong Liu Jingmiao Tian Lide Masayoshi Nakawo |
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| Institution: | College of Resources and Environment Sciences, Hunan Normal University, Changsha 410081;Chinese Academy of Meteorological Sciences, Beijing 100081,Laboratory of Ice and Cold Regions Environment, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000,Chinese Academy of Meteorological Sciences, Beijing 100081,Laboratory of Ice and Cold Regions Environment, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000,Research Institute for Humanity and Nature, Kyoto 602-0878, Japan |
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| Abstract: | 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 δ
18O 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, S
i, leads to the strengthening of the kinetic fractionation effect. The kinetic fractionation function makes the synthesis fractionation
factor decreased and the change of δ
18O 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 = bδ
18O+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 S
i. The greater the S
i, 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 ürümqi is simulated. The simulated stable isotopic ratio vs temperature and the δD vs δ
18O curves are very consistent with the actual regressions and MWL at ürümqi, respectively. |
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| Keywords: | stable isotopes fractionation kinetic effect temperature effect meteoric water line |
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