Update e_s to a more accurate formulation and add e_i (based on Murphy and Koop, 2005) #2480
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| @exporter.export | ||
| @preprocess_and_wrap(wrap_like='temperature') | ||
| @process_units({'temperature': '[temperature]'}, '[pressure]') |
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Perhaps
| @process_units({'temperature': '[temperature]'}, '[pressure]') | |
| @process_units({'temperature': 'kelvin'}, '[pressure]') |
to ensure it converts if someone passes Celsius or Fahrenheit? I should check whether the MetPy decorator works like the pint one.
| def test_ice_sat_vapor_pressure(): | ||
| """Test ice_saturation_vapor_pressure calculation.""" | ||
| temp = (np.arange(1, 38) * units.degC).to(units.degK) |
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Would it be worth parametrizing the test to pass temperature once in Kelvin and once in Celsius to ensure the conversion works properly? Something like:
| def test_ice_sat_vapor_pressure(): | |
| """Test ice_saturation_vapor_pressure calculation.""" | |
| temp = (np.arange(1, 38) * units.degC).to(units.degK) | |
| @pytest.mark.parametrize('unit', [units.degK, units.degC]) | |
| def test_ice_sat_vapor_pressure(unit): | |
| """Test ice_saturation_vapor_pressure calculation.""" | |
| temp = (np.arange(1, 38) * units.degC).to(unit) |
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I really appreciate the time you put into this contribution, and apologies on us not getting you prompt feedback. In the end, we implemented a newer approach to calculate saturation vapor pressure over liquid and ice based on Ambaum (2020) in #3726. Please feel free to reach out if there are still shortcomings in the implementation for your work. |
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Description Of Changes
In this pull request, I've modified the equilibrium vapor pressure (e_s) calculation to a more accurate formulation based on Murphy and Koop (2005; reference added). I've also added a method to calculate the ice equilibrium vapor pressure (e_i) based on the same manuscript as well as a unit test for this method. Different variations (using different input coefficients) of Teten's formula have been used in the literature (e.g., Bolton, 1980; Alduchov and Eskrige, 1996) but the use of the exponential form of this type of parameterization means that the fits are valid in a relatively limited range of temperatures. The MP2005 formulation on the other hand is valid for a much broader range of temperatures.
I was contemplating whether to add an optional input parameter to saturation_vapor_pressure for the water phase with a default to ice, but then thought that it might be better to add a separate method for ice, thus making code and documentation easier to follow.
Also, I would recommend using the "equilibrium vapor pressure" term rather than "saturation vapor pressure" as that is a more physically accurate term, but that would likely result in plenty of mess after changing the terminology and method terms.
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