alpha_equ_h2o

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alpha_equ_h2o#

Isotopic fractionation factors during liquid-water vapour equilibration.

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_equ_h2o(temp[, isotope, undef, eps, ...])

Isotopic fractionation factors during liquid-water vapour equilibration.
History

  • Written, Sep 2014, Matthias Cuntz

  • Code refactoring, Sep 2021, Matthias Cuntz

  • Tuple in/out, Oct 2021, Matthias Cuntz

  • Do not use masked arrays for undef to avoid overflow warning, Oct 2021, Matthias Cuntz

  • Bug masked array, need to check masked array before ndarray because the former is also the latter, Nov 2021, Matthias Cuntz

  • Bug if scalar, was still masked array, Jan 2022, Matthias Cuntz

  • Do not use astr in docstring examples, Jan 2022, Matthias Cuntz

  • More consistent docstrings, Jan 2022, Matthias Cuntz

  • Bug in return type if list or tuple and undef, Jan 2022, Matthias Cuntz

  • Change handling of return type to allow more (unspecific) iterable types such as pandas time series, Jan 2022, Matthias Cuntz

  • Return numpy array if type(input)(output) fails for unknown iterable types, Jan 2022, Matthias Cuntz

  • Use helper functions input2array and array2input, Jan 2022, Matthias Cuntz

alpha_equ_h2o(temp, isotope=None, undef=-9999.0, eps=False, greater1=True)[source]#

Isotopic fractionation factors during liquid-water vapour equilibration.

Calculates isotopic fractionation factors during liquid-water vapour equilibration at temperature temp [K]. It does not use the atmospheric convention, i.e. factor < 1, by default but sets factor > 1 (greater1=True).

Parameters:

  • temp (float or array-like) – Temperature [K]

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

  • undef (float, optional) – Exclude temp == undef from calculations (default: -9999.)

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

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

Returns:

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

Return type:

float or array-like

Notes

Majoube, M. (1971) Fractionnement en oxygene-18 entre la glace et la vapeur

d’eau Journal De Chimie Physique Et De Physico-Chimie Biologique, 68(4), 625-636.

Examples

Fractionation factors

>>> T0 = 273.15
>>> T  = np.array([0, 10., 15., 25.])
>>> print(np.around(alpha_equ_h2o(T+T0, isotope=0), 4))
[1. 1. 1. 1.]
>>> print(np.around(alpha_equ_h2o(T+T0, isotope=2), 4))
[1.0117 1.0107 1.0102 1.0094]
>>> print(np.around(alpha_equ_h2o(np.ma.array(T+T0, mask=(T==0.)),
...                               isotope=2, greater1=False), 4))
[-- 0.9894 0.9899 0.9907]

Fractionations

>>> print(np.around(alpha_equ_h2o(T+T0, isotope=1, eps=True)*1000., 4))
[112.3194 97.6829 91.1296 79.3443]
>>> print(np.around(alpha_equ_h2o(0.+T0, isotope=2, eps=True)*1000., 4))
11.7187
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