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Merge pull request #3242 from dcamron/rh-vapor-pressure
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@dopplershift
dopplershift authored Nov 3, 2023
2 parents c96b942 + 163702b commit 68baead
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Showing 4 changed files with 193 additions and 48 deletions.
2 changes: 2 additions & 0 deletions pyproject.toml
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Expand Up @@ -107,6 +107,8 @@ line-length = 95
exclude = ["docs", "build", "src/metpy/io/_metar_parser/metar_parser.py"]
select = ["A", "B", "C", "D", "E", "E226", "F", "G", "I", "N", "Q", "R", "S", "T", "U", "W"]
ignore = ["F405", "I001", "RET504", "RET505", "RET506", "RET507", "RUF100"]
preview = true
explicit-preview-rules = true

[tool.ruff.per-file-ignores]
"ci/filter_links.py" = ["E731", "T201", "S603", "S607"]
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150 changes: 114 additions & 36 deletions src/metpy/calc/thermo.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,8 @@
# Distributed under the terms of the BSD 3-Clause License.
# SPDX-License-Identifier: BSD-3-Clause
"""Contains a collection of thermodynamic calculations."""
from inspect import Parameter, Signature, signature

import numpy as np
import scipy.integrate as si
import scipy.optimize as so
Expand Down Expand Up @@ -55,15 +57,15 @@ def relative_humidity_from_dewpoint(temperature, dewpoint):
Notes
-----
.. math:: rh = \frac{e(T_d)}{e_s(T)}
.. math:: RH = \frac{e(T_d)}{e_s(T)}
.. versionchanged:: 1.0
Renamed ``dewpt`` parameter to ``dewpoint``
"""
e = saturation_vapor_pressure(dewpoint)
e_s = saturation_vapor_pressure(temperature)
return (e / e_s)
return e / e_s


@exporter.export
Expand Down Expand Up @@ -2026,28 +2028,33 @@ def mixing_ratio_from_relative_humidity(pressure, temperature, relative_humidity
>>> T = 28.1 * units.degC
>>> rh = .65
>>> mixing_ratio_from_relative_humidity(p, T, rh).to('g/kg')
<Quantity(15.9828362, 'gram / kilogram')>
<Quantity(15.7646969, 'gram / kilogram')>
See Also
--------
relative_humidity_from_mixing_ratio, saturation_mixing_ratio
Notes
-----
Formula adapted from [Hobbs1977]_ pg. 74.
Employs [WMO8]_ eq. 4.A.16 as derived from WMO relative humidity definition based on
vapor partial pressures (eq. 4.A.15).
.. math:: w = (rh)(w_s)
.. math:: RH = \frac{w}{\epsilon + w} \frac{\epsilon + w_s}{w_s}
.. math:: \therefore w = \frac{\epsilon * w_s * RH}{\epsilon + w_s (1 - RH)}
* :math:`w` is mixing ratio
* :math:`rh` is relative humidity as a unitless ratio
* :math:`w_s` is the saturation mixing ratio
* :math:`\epsilon` is the molecular weight ratio of vapor to dry air
* :math:`RH` is relative humidity as a unitless ratio
.. versionchanged:: 1.0
Changed signature from ``(relative_humidity, temperature, pressure)``
"""
return (relative_humidity
* saturation_mixing_ratio(pressure, temperature)).to('dimensionless')
w_s = saturation_mixing_ratio(pressure, temperature)
return (mpconsts.nounit.epsilon * w_s * relative_humidity
/ (mpconsts.nounit.epsilon + w_s * (1 - relative_humidity))).to('dimensionless')


@exporter.export
Expand Down Expand Up @@ -2081,27 +2088,31 @@ def relative_humidity_from_mixing_ratio(pressure, temperature, mixing_ratio):
>>> from metpy.units import units
>>> relative_humidity_from_mixing_ratio(1013.25 * units.hPa,
... 30 * units.degC, 18/1000).to('percent')
<Quantity(66.1763544, 'percent')>
<Quantity(67.1277085, 'percent')>
See Also
--------
mixing_ratio_from_relative_humidity, saturation_mixing_ratio
Notes
-----
Formula based on that from [Hobbs1977]_ pg. 74.
Employs [WMO8]_ eq. 4.A.16 as derived from WMO relative humidity definition based on
vapor partial pressures (eq. 4.A.15).
.. math:: rh = \frac{w}{w_s}
.. math:: RH = \frac{w}{\epsilon + w} \frac{\epsilon + w_s}{w_s}
* :math:`rh` is relative humidity as a unitless ratio
* :math:`w` is mixing ratio
* :math:`w_s` is the saturation mixing ratio
* :math:`\epsilon` is the molecular weight ratio of vapor to dry air
* :math:`RH` is relative humidity as a unitless ratio
.. versionchanged:: 1.0
Changed signature from ``(mixing_ratio, temperature, pressure)``
"""
return mixing_ratio / saturation_mixing_ratio(pressure, temperature)
w_s = saturation_mixing_ratio(pressure, temperature)
return (mixing_ratio / (mpconsts.nounit.epsilon + mixing_ratio)
* (mpconsts.nounit.epsilon + w_s) / w_s)


@exporter.export
Expand Down Expand Up @@ -2217,28 +2228,33 @@ def relative_humidity_from_specific_humidity(pressure, temperature, specific_hum
>>> from metpy.units import units
>>> relative_humidity_from_specific_humidity(1013.25 * units.hPa,
... 30 * units.degC, 18/1000).to('percent')
<Quantity(67.3893629, 'percent')>
<Quantity(68.3229304, 'percent')>
See Also
--------
relative_humidity_from_mixing_ratio
Notes
-----
Formula based on that from [Hobbs1977]_ pg. 74. and [Salby1996]_ pg. 118.
Employs [WMO8]_ eq. 4.A.16 as derived from WMO relative humidity definition based on
vapor partial pressures (eq. 4.A.15).
.. math:: RH = \frac{q}{(1-q)w_s}
.. math:: RH = \frac{w}{\epsilon + w} \frac{\epsilon + w_s}{w_s}
* :math:`RH` is relative humidity as a unitless ratio
* :math:`q` is specific humidity
given :math: w = \frac{q}{1-q}
* :math:`w` is mixing ratio
* :math:`w_s` is the saturation mixing ratio
* :math:`q` is the specific humidity
* :math:`\epsilon` is the molecular weight ratio of vapor to dry air
* :math:`RH` is relative humidity as a unitless ratio
.. versionchanged:: 1.0
Changed signature from ``(specific_humidity, temperature, pressure)``
"""
return (mixing_ratio_from_specific_humidity(specific_humidity)
/ saturation_mixing_ratio(pressure, temperature))
return relative_humidity_from_mixing_ratio(
pressure, temperature, mixing_ratio_from_specific_humidity(specific_humidity))


@exporter.export
Expand Down Expand Up @@ -3544,7 +3560,7 @@ def thickness_hydrostatic_from_relative_humidity(pressure, temperature, relative
>>> thickness_hydrostatic_from_relative_humidity(p[ip1000_500],
... T[ip1000_500],
... rh[ip1000_500])
<Quantity(5781.35394, 'meter')>
<Quantity(5781.16001, 'meter')>
See Also
--------
Expand Down Expand Up @@ -3857,21 +3873,16 @@ def static_stability(pressure, temperature, vertical_dim=0):


@exporter.export
@preprocess_and_wrap(
wrap_like='temperature',
broadcast=('pressure', 'temperature', 'specific_humidity')
)
@check_units('[pressure]', '[temperature]', '[dimensionless]')
def dewpoint_from_specific_humidity(pressure, temperature, specific_humidity):
r"""Calculate the dewpoint from specific humidity, temperature, and pressure.
def dewpoint_from_specific_humidity(*args, **kwargs):
r"""Calculate the dewpoint from specific humidity and pressure.
Parameters
----------
pressure: `pint.Quantity`
Total atmospheric pressure
temperature: `pint.Quantity`
Air temperature
temperature: `pint.Quantity`, optional
Air temperature. Unused in calculation, pending deprecation
specific_humidity: `pint.Quantity`
Specific humidity of air
Expand All @@ -3885,20 +3896,87 @@ def dewpoint_from_specific_humidity(pressure, temperature, specific_humidity):
--------
>>> from metpy.calc import dewpoint_from_specific_humidity
>>> from metpy.units import units
>>> dewpoint_from_specific_humidity(1000 * units.hPa, 10 * units.degC, 5 * units('g/kg'))
<Quantity(3.73203192, 'degree_Celsius')>
>>> dewpoint_from_specific_humidity(1000 * units.hPa, 5 * units('g/kg'))
<Quantity(3.79314079, 'degree_Celsius')>
.. versionchanged:: 1.6
Made `temperature` arg optional, to be deprecated
.. versionchanged:: 1.0
Changed signature from ``(specific_humidity, temperature, pressure)``
See Also
--------
relative_humidity_from_mixing_ratio, dewpoint_from_relative_humidity
relative_humidity_from_mixing_ratio, dewpoint_from_relative_humidity, dewpoint
Notes
-----
Employs [WMO8]_ eq 4.A.6,
.. math:: e = \frac{w}{\epsilon + w} p
with
.. math:: w = \frac{q}{1-q}
* :math:`q` is specific humidity
* :math:`w` is mixing ratio
* :math:`\epsilon` is the molecular weight ratio of vapor to dry air
to calculate vapor partial pressure :math:`e` for dewpoint calculation input. See
:func:`~dewpoint` for additional information.
"""
return dewpoint_from_relative_humidity(temperature,
relative_humidity_from_specific_humidity(
pressure, temperature, specific_humidity))
sig = Signature([Parameter('pressure', Parameter.POSITIONAL_OR_KEYWORD),
Parameter('temperature', Parameter.POSITIONAL_OR_KEYWORD),
Parameter('specific_humidity', Parameter.POSITIONAL_OR_KEYWORD)])

try:
bound_args = sig.bind(*args, **kwargs)
_warnings.warn(
'Temperature argument is unused and will be deprecated in a future version.',
PendingDeprecationWarning)
except TypeError:
sig = signature(_dewpoint_from_specific_humidity)
bound_args = sig.bind(*args, **kwargs)

return _dewpoint_from_specific_humidity(bound_args.arguments['pressure'],
bound_args.arguments['specific_humidity'])


@preprocess_and_wrap(
wrap_like='specific_humidity',
broadcast=('specific_humidity', 'pressure')
)
@check_units(pressure='[pressure]', specific_humidity='[dimensionless]')
def _dewpoint_from_specific_humidity(pressure, specific_humidity):
r"""Calculate the dewpoint from specific humidity and pressure.
See :func:`~dewpoint_from_specific_humidity` for more information. This implementation
is provided internally to preserve backwards compatibility with MetPy<1.6.
Parameters
----------
pressure: `pint.Quantity`
Total atmospheric pressure
specific_humidity: `pint.Quantity`
Specific humidity of air
Returns
-------
`pint.Quantity`
Dew point temperature
.. versionchanged:: 1.6
Made `temperature` arg optional, to be deprecated
.. versionchanged:: 1.0
Changed signature from ``(specific_humidity, temperature, pressure)``
"""
w = mixing_ratio_from_specific_humidity(specific_humidity)
e = pressure * w / (mpconsts.nounit.epsilon + w)

return dewpoint(e)


@exporter.export
Expand Down
10 changes: 5 additions & 5 deletions src/metpy/units.py
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Original file line number Diff line number Diff line change
Expand Up @@ -249,10 +249,10 @@ def _check_argument_units(args, defaults, dimensionality):
yield arg, val, 'none', need


def _get_changed_version(docstring):
def _get_changed_versions(docstring):
"""Find the most recent version in which the docs say a function changed."""
matches = re.findall(r'.. versionchanged:: ([\d.]+)', docstring)
return max(matches) if matches else None
return matches


def _check_units_outer_helper(func, *args, **kwargs):
Expand Down Expand Up @@ -302,10 +302,10 @@ def _check_units_inner_helper(func, sig, defaults, dims, *args, **kwargs):

# If function has changed, mention that fact
if func.__doc__:
changed_version = _get_changed_version(func.__doc__)
if changed_version:
changed_versions = _get_changed_versions(func.__doc__)
if changed_versions:
msg = (
f'This function changed in {changed_version}--double check '
f'This function changed in version(s) {changed_versions}--double check '
'that the function is being called properly.\n'
) + msg
raise ValueError(msg)
Expand Down
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