alpha_kin_h2o

Contents

alpha_kin_h2o#

Kinetic fractionation factors for molecular diffusion of water isotopologues.

This module was written by Matthias Cuntz while at Department of Computational Hydrosystems, Helmholtz Centre for Environmental Research - UFZ, Leipzig, Germany, and continued while at Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Nancy, France.

copyright:

Copyright 2014-2022 Matthias Cuntz, see AUTHORS.rst for details.

license:

MIT License, see LICENSE for details.

The following functions are provided:

alpha_kin_h2o([isotope, eps, greater1, ...])

Kinetic fractionation factors for molecular diffusion of water isotopologues.
History

  • Written, Sep 2014, Matthias Cuntz

  • Code refactoring, Nov 2021, Matthias Cuntz

  • More consistent docstrings, Jan 2022, Matthias Cuntz

alpha_kin_h2o(isotope=None, eps=False, greater1=True, boundary=False, cappa=False)[source]#

Kinetic fractionation factors for molecular diffusion of water isotopologues.

It does not use the atmospheric convention, i.e. factor < 1, by default but sets factor > 1 (greater1=True).

Parameters:

  • isotope (int, optional) – Select water isotopologue: 1: HDO; 2: H218O; else: no fractionation, i.e. return 1 (default)

  • eps (bool, optional) – Returns fractionation epsilon=alpha-1 instead of fractionation factor alpha if True (default: return alpha)

  • greater1 (bool, optional) – alpha > 1 if True, which is not the atmospheric convention. alpha < 1 if False, which is the atmospheric convention.

  • boundary (bool, optional) – Returns alpha**2/3 for diffusion through boundary layer instead of molecular diffusion if True (default: False).

  • cappa (bool, optional) – Uses factors of Cappa et al. (2003) instead of Merlivat (1978) if True (default: False).

Returns:

alpha / epsilon – Kinetic fractionation factor (alpha) or fractionation (epsilon)

Return type:

float or array-like

Notes

Cappa, C. D., Hendricks, M. B., DePaolo, D. J., & Cohen, R. (2003)

Isotopic fractionation of water during evaporation Journal of Geophysical Research, 108(D16), 4525. doi:10.1029/2003JD003597

Merlivat, L. (1978)

Molecular Diffusivities Of (H2O)-O-16 HD16O, And (H2O)-O-18 In Gases, The Journal of Chemical Physics, 69(6), 2864-2871.

Merlivat, L., & Jouzel, J. (1979)

Global climatic interpretation of the deuterium-oxygen-18 relationship for precipitation, Journal of Geophysical Research, 84(C8), 5029-5033.

Examples

Fractionation factor

>>> import numpy as np
>>> print(np.around(alpha_kin_h2o(isotope=0), 4))
1.0

Fractionations

>>> print(np.around(alpha_kin_h2o(isotope=1, eps=True)*1000., 4))
25.1153
>>> print(np.around(alpha_kin_h2o(isotope=2, eps=True,
...                               greater1=False)*1000., 4))
-27.3
>>> print(np.around(alpha_kin_h2o(isotope=2, eps=True, greater1=True,
...                               boundary=True)*1000., 4))
18.6244
>>> print(np.around(alpha_kin_h2o(isotope=2, eps=True, greater1=False,
...                               boundary=True, cappa=True)*1000., 4))
-20.7076
Contents