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meteorology.py
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meteorology.py
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import dask.array as da
import numpy as np
import typing
import warnings
import xarray as xr
from .gc_util import _generate_wrapper_docstring
def _dewtemp(
tk: typing.Union[np.ndarray, xr.DataArray, list,
float], rh: typing.Union[np.ndarray, xr.DataArray, list,
float]
) -> typing.Union[np.ndarray, xr.DataArray, list, float]:
"""This function calculates the dew point temperature given temperature and
relative humidity using equations from John Dutton's "Ceaseless Wind" (pp
273-274)
Parameters
----------
tk : ndarray, :class:`xarray.DataArray`, :obj:`list`, or :obj:`float`
Temperature in Kelvin
rh : ndarray, :class:`xarray.DataArray`, :obj:`list`, or :obj:`float`
Relative humidity. Must be the same dimensions as ``temperature``
Returns
-------
tdk : ndarray, :class:`xarray.DataArray`, :obj:`list`, or :obj:`float`
Dewpoint temperature in Kelvin. Same size as input variable temperature
See Also
--------
Related GeoCAT Functions:
:func:`dewtemp`
Related NCL Functions:
`dewtemp_trh <https://www.ncl.ucar.edu/Document/Functions/Built-in/dewtemp_trh.shtml>`__
"""
gc = 461.5 # gas constant for water vapor [j/{kg-k}]
gcx = gc / (1000 * 4.186) # [cal/{g-k}]
lhv = (597.3 - 0.57 * (tk - 273)) / gcx
tdk = tk * lhv / (lhv - tk * np.log(rh * 0.01))
return tdk
def _heat_index(temperature: np.ndarray,
relative_humidity: typing.Union[np.ndarray, xr.DataArray, list,
float],
alternate_coeffs: bool = False) -> np.ndarray:
"""Compute the 'heat index' as calculated by the National Weather Service.
Internal function for heat_index
Parameters
----------
temperature : ndarray
temperature(s) in Fahrenheit
relative_humidity : ndarray, :class:`xarray.DataArray`, :class:`list`, :class:`float`
relative humidity as a percentage. Must be the same shape as
``temperature``
alternate_coeffs : bool, optional
flag to use alternate set of coefficients appropriate for
temperatures from 70F to 115F and humidities between 0% and 80%
Returns
-------
heatindex : ndarray
Calculated heat index. Same shape as ``temperature``
See Also
--------
Related GeoCAT Functions:
:func:`heat_index`,
:func:`_xheat_index`
Related NCL Functions:
`heat_index_nws <https://www.ncl.ucar.edu/Document/Functions/Contributed/heat_index_nws.shtml>`__
"""
# Default coefficients for (t>=80F) and (40<gh<100)
coeffs = [
-42.379, 2.04901523, 10.14333127, -0.22475541, -0.00683783, -0.05481717,
0.00122874, 0.00085282, -0.00000199
]
crit = [80, 40, 100] # [T_low [F], RH_low, RH_high]
# optional flag coefficients for (70F<t<115F) and (0<gh<80)
# within 3F of default coeffs
if alternate_coeffs:
coeffs = [
0.363445176, 0.988622465, 4.777114035, -0.114037667, -0.000850208,
-0.020716198, 0.000687678, 0.000274954, 0.0
]
crit = [70, 0, 80] # [T_low [F], RH_low, RH_high]
# NWS practice
# average Steadman and t
heatindex = (0.5 * (temperature + 61.0 + ((temperature - 68.0) * 1.2) +
(relative_humidity * 0.094)) + temperature) * 0.5
# http://ehp.niehs.nih.gov/1206273/
heatindex = xr.where(temperature < 40, temperature, heatindex)
# if all t values less than critical, return hi
# otherwise perform calculation
eqtype = 0
if not all(temperature.ravel() < crit[0]):
eqtype = 1
heatindex = xr.where(heatindex > crit[0],
_nws_eqn(coeffs, temperature, relative_humidity),
heatindex)
# adjustments
heatindex = xr.where(
np.logical_and(relative_humidity < 13,
np.logical_and(temperature > 80, temperature < 112)),
heatindex - ((13 - relative_humidity) / 4) * np.sqrt(
(17 - abs(temperature - 95)) / 17), heatindex)
heatindex = xr.where(
np.logical_and(relative_humidity > 85,
np.logical_and(temperature > 80, temperature < 87)),
heatindex + ((relative_humidity - 85.0) / 10.0) *
((87.0 - temperature) / 5.0), heatindex)
return heatindex
def _nws_eqn(coeffs, temp, rel_hum):
"""Helper function to compute the heat index.
Internal function for heat_index
Parameters
----------
coeffs : ndarray
coefficients to calculate heat index
temp : ndarray, :class:`xarray.DataArray`, :class:`list`, :class:`float`
temperature
rel_hum : ndarray, :class:`xarray.DataArray`, :class:`list`, :class:`float`
relative humidity as a percentage. Must be the same shape as
``temperature``
Returns
-------
heatindex : ndarray, :class:`xarray.DataArray`, :class:`list`, :class:`float`
Intermediate calculated heat index. Same shape as ``temperature``
See Also
--------
Related GeoCAT Functions:
:func:`heat_index`,
:func:`_heat_index`
Related NCL Functions:
`heat_index_nws <https://www.ncl.ucar.edu/Document/Functions/Contributed/heat_index_nws.shtml>`__,
"""
heatindex = coeffs[0] \
+ coeffs[1] * temp \
+ coeffs[2] * rel_hum \
+ coeffs[3] * temp * rel_hum \
+ coeffs[4] * temp ** 2 \
+ coeffs[5] * rel_hum ** 2 \
+ coeffs[6] * temp ** 2 * rel_hum \
+ coeffs[7] * temp * rel_hum ** 2 \
+ coeffs[8] * temp ** 2 * rel_hum ** 2
return heatindex
def _relhum(
t: typing.Union[np.ndarray, list, float],
w: typing.Union[np.ndarray, xr.DataArray, list,
float], p: typing.Union[np.ndarray, xr.DataArray, list,
float]) -> np.ndarray:
"""Calculates relative humidity with respect to ice, given temperature,
mixing ratio, and pressure.
"Improved Magnus' Form Approx. of Saturation Vapor pressure"
Oleg A. Alduchov and Robert E. Eskridge
https://journals.ametsoc.org/view/journals/apme/35/4/1520-0450_1996_035_0601_imfaos_2_0_co_2.xml
Parameters
----------
t : ndarray, :obj:`list`, or :obj:`float`
Temperature in Kelvin
w : ndarray, :class:`xarray.DataArray`, :obj:`list`, or :obj:`float`
Mixing ratio in kg/kg. Must have the same dimensions as ``temperature``
p : ndarray, :class:`xarray.DataArray`, :obj:`list`, or :obj:`float`
Pressure in Pa. Must have the same dimensions as ``temperature``
Returns
-------
rh : ndarray
Relative humidity. Will have the same dimensions as ``temperature``
See Also
--------
Related GeoCAT Functions:
:func:`relhum`
:func:`relhum_ice`
:func:`relhum_water`
:func:`_xrelhum`
Related NCL Functions:
`relhum <https://www.ncl.ucar.edu/Document/Functions/Built-in/relhum.shtml>`__,
`relhum_ttd <https://www.ncl.ucar.edu/Document/Functions/Contributed/relhum_ttd.shtml>`__,
`relhum_ice <https://www.ncl.ucar.edu/Document/Functions/Built-in/relhum_ice.shtml>`__,
`relhum_water <https://www.ncl.ucar.edu/Document/Functions/Built-in/relhum_water.shtml>`__
"""
table = np.asarray([
0.01403, 0.01719, 0.02101, 0.02561, 0.03117, 0.03784, 0.04584, 0.05542,
0.06685, 0.08049, 0.09672, 0.1160, 0.1388, 0.1658, 0.1977, 0.2353,
0.2796, 0.3316, 0.3925, 0.4638, 0.5472, 0.6444, 0.7577, 0.8894, 1.042,
1.220, 1.425, 1.662, 1.936, 2.252, 2.615, 3.032, 3.511, 4.060, 4.688,
5.406, 6.225, 7.159, 8.223, 9.432, 10.80, 12.36, 14.13, 16.12, 18.38,
20.92, 23.80, 27.03, 30.67, 34.76, 39.35, 44.49, 50.26, 56.71, 63.93,
71.98, 80.97, 90.98, 102.1, 114.5, 128.3, 143.6, 160.6, 179.4, 200.2,
223.3, 248.8, 276.9, 307.9, 342.1, 379.8, 421.3, 466.9, 517.0, 572.0,
632.3, 698.5, 770.9, 850.2, 937.0, 1032.0, 1146.6, 1272.0, 1408.1,
1556.7, 1716.9, 1890.3, 2077.6, 2279.6, 2496.7, 2729.8, 2980.0, 3247.8,
3534.1, 3839.8, 4164.8, 4510.5, 4876.9, 5265.1, 5675.2, 6107.8, 6566.2,
7054.7, 7575.3, 8129.4, 8719.2, 9346.50, 10013.0, 10722.0, 11474.0,
12272.0, 13119.0, 14017.0, 14969.0, 15977.0, 17044.0, 18173.0, 19367.0,
20630.0, 21964.0, 23373.0, 24861.0, 26430.0, 28086.0, 29831.0, 31671.0,
33608.0, 35649.0, 37796.0, 40055.0, 42430.0, 44927.0, 47551.0, 50307.0,
53200.0, 56236.0, 59422.0, 62762.0, 66264.0, 69934.0, 73777.0, 77802.0,
82015.0, 86423.0, 91034.0, 95855.0, 100890.0, 106160.0, 111660.0,
117400.0, 123400.0, 129650.0, 136170.0, 142980.0, 150070.0, 157460.0,
165160.0, 173180.0, 181530.0, 190220.0, 199260.0, 208670.0, 218450.0,
228610.0, 239180.0, 250160.0, 261560.0, 273400.0, 285700.0, 298450.0,
311690.0, 325420.0, 339650.0, 354410.0, 369710.0, 385560.0, 401980.0,
418980.0, 436590.0, 454810.0, 473670.0, 493170.0, 513350.0, 534220.0,
555800.0, 578090.0, 601130.0, 624940.0, 649530.0, 674920.0, 701130.0,
728190.0, 756110.0, 784920.0, 814630.0, 845280.0, 876880.0, 909450.0,
943020.0, 977610.0, 1013250.0, 1049940.0, 1087740.0, 1087740.
])
maxtemp = 375.16
mintemp = 173.16
# replace values of t above and below max and min values for temperature
t = np.clip(t, mintemp, maxtemp)
it = (t - mintemp).astype(int)
t2 = mintemp + it
es = (t2 + 1 - t) * table[it] + (t - t2) * table[it + 1]
es = es * 0.1
rh = (w * (p - 0.378 * es) / (0.622 * es)) * 100
# if any value is below 0.0001, set to 0.0001
rh = np.clip(rh, 0.0001, None)
return rh
def _relhum_ice(t: typing.Union[np.ndarray, list, float],
w: typing.Union[np.ndarray, list, float],
p: typing.Union[np.ndarray, list, float]) -> np.ndarray:
"""Calculates relative humidity with respect to ice, given temperature,
mixing ratio, and pressure.
"Improved Magnus' Form Approx. of Saturation Vapor pressure"
Oleg A. Alduchov and Robert E. Eskridge
https://journals.ametsoc.org/view/journals/apme/35/4/1520-0450_1996_035_0601_imfaos_2_0_co_2.xml
Parameters
----------
t : ndarray, :obj:`list`, :obj:`float`
Temperature in Kelvin
w : ndarray, :obj:`list`, :obj:`float`
Mixing ratio in kg/kg. Must have the same dimensions as ``temperature``
p : ndarray, :obj:`list`, :obj:`float`
Pressure in Pa. Must have the same dimensions as ``temperature``
Returns
-------
rh : ndarray
Relative humidity. Will have the same dimensions as ``temperature``
See Also
--------
Related GeoCAT Functions:
:func:`relhum`
:func:`relhum_ice`
:func:`relhum_water`
:func:`_xrelhum`
Related NCL Functions:
`relhum <https://www.ncl.ucar.edu/Document/Functions/Built-in/relhum.shtml>`__,
`relhum_ttd <https://www.ncl.ucar.edu/Document/Functions/Contributed/relhum_ttd.shtml>`__,
`relhum_ice <https://www.ncl.ucar.edu/Document/Functions/Built-in/relhum_ice.shtml>`__,
`relhum_water <https://www.ncl.ucar.edu/Document/Functions/Built-in/relhum_water.shtml>`__
"""
# Define data variables
t0 = 273.15
ep = 0.622
onemep = 0.378
es0 = 6.1128
a = 22.571
b = 273.71
est = es0 * np.exp((a * (t - t0)) / ((t - t0) + b))
qst = (ep * est) / ((p * 0.01) - onemep * est)
rh = 100 * (w / qst)
return rh
def _relhum_water(t: typing.Union[np.ndarray, list, float],
w: typing.Union[np.ndarray, list, float],
p: typing.Union[np.ndarray, list, float]) -> np.ndarray:
"""Calculates relative humidity with respect to water, given temperature,
mixing ratio, and pressure.
Definition of mixing ratio if:
- ``es`` - is the saturation mixing ratio
- ``ep`` - is the ratio of the molecular weights of water vapor to dry air
- ``p`` - is the atmospheric pressure
- ``rh`` - is the relative humidity (given as a percent)
.. math::
rh = 100* q / ( (ep*es)/(p-es) )
Parameters
----------
t : ndarray, :obj:`list`, :obj:`float`
Temperature in Kelvin
w : ndarray, :obj:`list`, :obj:`float`
Mixing ratio in kg/kg. Must have the same dimensions as ``temperature``
p : ndarray, :obj:`list`, :obj:`float`
Pressure in Pa. Must have the same dimensions as ``temperature``
Returns
-------
rh : ndarray
Relative humidity. Will have the same dimensions as ``temperature``
See Also
--------
Related GeoCAT Functions:
:func:`relhum`
:func:`relhum_ice`
:func:`relhum_water`
:func:`_xrelhum`
Related NCL Functions:
`relhum <https://www.ncl.ucar.edu/Document/Functions/Built-in/relhum.shtml>`__,
`relhum_ttd <https://www.ncl.ucar.edu/Document/Functions/Contributed/relhum_ttd.shtml>`__,
`relhum_ice <https://www.ncl.ucar.edu/Document/Functions/Built-in/relhum_ice.shtml>`__,
`relhum_water <https://www.ncl.ucar.edu/Document/Functions/Built-in/relhum_water.shtml>`__
"""
# Define data variables
t0 = 273.15
ep = 0.622
onemep = 0.378
es0 = 6.1128
a = 17.269
b = 35.86
est = es0 * np.exp((a * (t - t0)) / (t - b))
qst = (ep * est) / ((p * 0.01) - onemep * est)
rh = 100 * (w / qst)
return rh
def _xheat_index(temperature: xr.DataArray,
relative_humidity: xr.DataArray,
alternate_coeffs: bool = False) -> tuple([xr.DataArray, int]):
"""Compute the 'heat index' as calculated by the National Weather Service.
Internal function for heat_index for dask
Parameters
----------
temperature : :class:`xarray.DataArray`
temperature(s) in Fahrenheit
relative_humidity : :class:`xarray.DataArray`
relative humidity as a percentage. Must be the same shape as
``temperature``
alternate_coeffs : bool, optional
flag to use alternate set of coefficients appropriate for
temperatures from 70F to 115F and humidities between 0% and 80%
Returns
-------
heatindex : :class:`xarray.DataArray`
Calculated heat index. Same shape as ``temperature``
eqtype : :class:`int`
version of equations used, for xarray attrs output
See Also
--------
Related GeoCAT Functions:
:func:`heat_index`
:func:`_heat_index`
Related NCL Functions:
`heat_index_nws <https://www.ncl.ucar.edu/Document/Functions/Contributed/heat_index_nws.shtml>`__,
"""
# Default coefficients for (t>=80F) and (40<gh<100)
coeffs = [
-42.379, 2.04901523, 10.14333127, -0.22475541, -0.00683783, -0.05481717,
0.00122874, 0.00085282, -0.00000199
]
crit = [80, 40, 100] # [T_low [F], RH_low, RH_high]
# optional flag coefficients for (70F<t<115F) and (0<gh<80)
# within 3F of default coeffs
if alternate_coeffs:
coeffs = [
0.363445176, 0.988622465, 4.777114035, -0.114037667, -0.000850208,
-0.020716198, 0.000687678, 0.000274954, 0.0
]
crit = [70, 0, 80] # [T_low [F], RH_low, RH_high]
# NWS practice
# average Steadman and t
heatindex = (0.5 * (temperature + 61.0 + ((temperature - 68.0) * 1.2) +
(relative_humidity * 0.094)) + temperature) * 0.5
# http://ehp.niehs.nih.gov/1206273/
heatindex = xr.where(temperature < 40, temperature, heatindex)
# if all t values less than critical, return hi
# otherwise perform calculation
eqtype = 0
if not all(temperature.data.ravel() < crit[0]):
eqtype = 1
heatindex = xr.where(heatindex > crit[0],
_nws_eqn(coeffs, temperature, relative_humidity),
heatindex)
# adjustments
heatindex = xr.where(
np.logical_and(relative_humidity < 13,
np.logical_and(temperature > 80, temperature < 112)),
heatindex - ((13 - relative_humidity) / 4) * np.sqrt(
(17 - abs(temperature - 95)) / 17), heatindex)
heatindex = xr.where(
np.logical_and(relative_humidity > 85,
np.logical_and(temperature > 80, temperature < 87)),
heatindex + ((relative_humidity - 85.0) / 10.0) *
((87.0 - temperature) / 5.0), heatindex)
return heatindex, eqtype
def _xrelhum(t: xr.DataArray, w: xr.DataArray, p: xr.DataArray) -> xr.DataArray:
"""Calculates relative humidity with respect to ice, given temperature,
mixing ratio, and pressure.
"Improved Magnus' Form Approx. of Saturation Vapor pressure"
Oleg A. Alduchov and Robert E. Eskridge
https://journals.ametsoc.org/view/journals/apme/35/4/1520-0450_1996_035_0601_imfaos_2_0_co_2.xml
Parameters
----------
t : :class:`xarray.DataArray`
Temperature in Kelvin
w : :class:`xarray.DataArray`
Mixing ratio in kg/kg. Must have the same dimensions as ``temperature``
p : :class:`xarray.DataArray`
Pressure in Pa. Must have the same dimensions as ``temperature``
Returns
-------
rh : :class:`xarray.DataArray`
Relative humidity. Will have the same dimensions as ``temperature``
See Also
--------
Related GeoCAT Functions:
:func:`relhum`
:func:`relhum_ice`
:func:`relhum_water`
Related NCL Functions:
`relhum <https://www.ncl.ucar.edu/Document/Functions/Built-in/relhum.shtml>`__,
`relhum_ttd <https://www.ncl.ucar.edu/Document/Functions/Contributed/relhum_ttd.shtml>`__,
`relhum_ice <https://www.ncl.ucar.edu/Document/Functions/Built-in/relhum_ice.shtml>`__,
`relhum_water <https://www.ncl.ucar.edu/Document/Functions/Built-in/relhum_water.shtml>`__
"""
table = da.from_array([
0.01403, 0.01719, 0.02101, 0.02561, 0.03117, 0.03784, 0.04584, 0.05542,
0.06685, 0.08049, 0.09672, 0.1160, 0.1388, 0.1658, 0.1977, 0.2353,
0.2796, 0.3316, 0.3925, 0.4638, 0.5472, 0.6444, 0.7577, 0.8894, 1.042,
1.220, 1.425, 1.662, 1.936, 2.252, 2.615, 3.032, 3.511, 4.060, 4.688,
5.406, 6.225, 7.159, 8.223, 9.432, 10.80, 12.36, 14.13, 16.12, 18.38,
20.92, 23.80, 27.03, 30.67, 34.76, 39.35, 44.49, 50.26, 56.71, 63.93,
71.98, 80.97, 90.98, 102.1, 114.5, 128.3, 143.6, 160.6, 179.4, 200.2,
223.3, 248.8, 276.9, 307.9, 342.1, 379.8, 421.3, 466.9, 517.0, 572.0,
632.3, 698.5, 770.9, 850.2, 937.0, 1032.0, 1146.6, 1272.0, 1408.1,
1556.7, 1716.9, 1890.3, 2077.6, 2279.6, 2496.7, 2729.8, 2980.0, 3247.8,
3534.1, 3839.8, 4164.8, 4510.5, 4876.9, 5265.1, 5675.2, 6107.8, 6566.2,
7054.7, 7575.3, 8129.4, 8719.2, 9346.50, 10013.0, 10722.0, 11474.0,
12272.0, 13119.0, 14017.0, 14969.0, 15977.0, 17044.0, 18173.0, 19367.0,
20630.0, 21964.0, 23373.0, 24861.0, 26430.0, 28086.0, 29831.0, 31671.0,
33608.0, 35649.0, 37796.0, 40055.0, 42430.0, 44927.0, 47551.0, 50307.0,
53200.0, 56236.0, 59422.0, 62762.0, 66264.0, 69934.0, 73777.0, 77802.0,
82015.0, 86423.0, 91034.0, 95855.0, 100890.0, 106160.0, 111660.0,
117400.0, 123400.0, 129650.0, 136170.0, 142980.0, 150070.0, 157460.0,
165160.0, 173180.0, 181530.0, 190220.0, 199260.0, 208670.0, 218450.0,
228610.0, 239180.0, 250160.0, 261560.0, 273400.0, 285700.0, 298450.0,
311690.0, 325420.0, 339650.0, 354410.0, 369710.0, 385560.0, 401980.0,
418980.0, 436590.0, 454810.0, 473670.0, 493170.0, 513350.0, 534220.0,
555800.0, 578090.0, 601130.0, 624940.0, 649530.0, 674920.0, 701130.0,
728190.0, 756110.0, 784920.0, 814630.0, 845280.0, 876880.0, 909450.0,
943020.0, 977610.0, 1013250.0, 1049940.0, 1087740.0, 1087740.
])
maxtemp = 375.16
mintemp = 173.16
# replace values of t above and below max and min values for temperature
t = t.clip(mintemp, maxtemp)
it = (t - mintemp).astype(int).data
t2 = mintemp + it
it_shape = it.shape
es = (t2 + 1 - t) * table[it.ravel()].reshape(it_shape) + (
t - t2) * table[it.ravel() + 1].reshape(it_shape)
es = es * 0.1
rh = (w * (p - 0.378 * es) / (0.622 * es)) * 100
rh = rh.clip(0.0001, None)
return rh
def dewtemp(
temperature: typing.Union[np.ndarray, xr.DataArray, list, float],
relative_humidity: typing.Union[np.ndarray, xr.DataArray, list, float]
) -> typing.Union[np.ndarray, float]:
"""This function calculates the dew point temperature given temperature and
relative humidity using equations from John Dutton's "Ceaseless Wind" (pp
273-274)
Parameters
----------
temperature : ndarray, :class:`xarray.DataArray`, :obj:`list`, or :obj:`float`
Temperature in Kelvin
relative_humidity : ndarray, :class:`xarray.DataArray`, :obj:`list`, or :obj:`float`
Relative humidity. Must be the same dimensions as ``temperature``
Returns
-------
dew_pnt_temp : ndarray or :obj:`float`
Dewpoint temperature in Kelvin. Same size as input variable temperature
See Also
--------
Related GeoCAT Functions:
:func:`_dewtemp`
Related NCL Functions:
`dewtemp_trh <https://www.ncl.ucar.edu/Document/Functions/Built-in/dewtemp_trh.shtml>`__
"""
inputs = [temperature, relative_humidity]
# ensure all inputs same size
if not (np.shape(x) == np.shape(inputs[0]) for x in inputs):
raise ValueError("dewtemp: dimensions of inputs are not the same")
# Get input types
in_types = [type(item) for item in inputs]
if xr.DataArray in in_types:
# check all inputs are xarray.DataArray
if any(x != xr.DataArray for x in in_types):
raise TypeError(
"relhum: if using xarray, all inputs must be xarray")
# call internal computation function
# note: no alternative internal function required for dewtemp
dew_pnt_temp = _dewtemp(temperature, relative_humidity)
# set xarray attributes
dew_pnt_temp.attrs['long_name'] = 'dew point temperature'
dew_pnt_temp.attrs['units'] = 'Kelvin'
else:
# ensure in numpy array for function call
temperature = np.asarray(temperature)
relative_humidity = np.asarray(relative_humidity)
# function call for non-dask/xarray
dew_pnt_temp = _dewtemp(temperature, relative_humidity)
return dew_pnt_temp
def heat_index(
temperature: typing.Union[np.ndarray, xr.DataArray, list, float],
relative_humidity: typing.Union[np.ndarray, xr.DataArray, list, float],
alternate_coeffs: bool = False
) -> typing.Union[np.ndarray, xr.DataArray]:
"""Compute the 'heat index' as calculated by the National Weather Service.
The heat index calculation in this function is described at:
https://www.wpc.ncep.noaa.gov/html/heatindex_equation.shtml
The 'Heat Index' is a measure of how hot weather "feels" to the body. The combination of temperature and humidity
produce an "apparent temperature" or the temperature the body "feels". The returned values are for shady
locations only. Exposure to full sunshine can increase heat index values by up to 15°F. Also, strong winds,
particularly with very hot, dry air, can be extremely hazardous as the wind adds heat to the body
The computation of the heat index is a refinement of a result obtained by multiple regression analysis carried
out by Lans P. Rothfusz and described in a 1990 National Weather Service (NWS) Technical Attachment (SR 90-23).
All values less that 40F/4.4C/277.65K are set to the ambient temperature.
In practice, the Steadman formula is computed first and the result averaged with the temperature. If this heat
index value is 80 degrees F or higher, the full regression equation along with any adjustment as described above
is applied. If the ambient temperature is less the 40F (4.4C/277.65K), the heat index is set to the ambient
temperature.
Parameters
----------
temperature : ndarray, :class:`xarray.DataArray`, :class:`list`, :class:`float`
temperature(s) in Fahrenheit
relative_humidity : ndarray, :class:`xarray.DataArray`, :class:`list`, :class:`float`
relative humidity as a percentage. Must be the same shape as
``temperature``
alternate_coeffs : bool, optional
flag to use alternate set of coefficients appropriate for
temperatures from 70F to 115F and humidities between 0% and 80%
Returns
-------
heatindex : ndarray, :class:`xarray.DataArray`
Calculated heat index. Same shape as ``temperature``
Examples
--------
>>> import numpy as np
>>> import geocat.comp
>>> t = np.array([104, 100, 92])
>>> rh = np.array([55, 65, 60])
>>> hi = heat_index(t,rh)
>>> hi
array([137.36135724, 135.8679973 , 104.68441864])
See Also
--------
Related GeoCAT Functions:
:func:`_heat_index`
:func:`_xheat_index`
Related NCL Functions:
`heat_index_nws <https://www.ncl.ucar.edu/Document/Functions/Contributed/heat_index_nws.shtml>`__
"""
inputs = [temperature, relative_humidity]
# ensure all inputs same size
if not (np.shape(x) == np.shape(inputs[0]) for x in inputs):
raise ValueError("heat_index: dimensions of inputs are not the same")
# Get input types
in_types = [type(item) for item in inputs]
# run dask compatible version if input is xarray
if xr.DataArray in in_types:
# check all inputs are xarray.DataArray
if not all(x == xr.DataArray for x in in_types):
raise TypeError(
"heat_index: if using xarray, all inputs must be xarray")
# input validation on relative humidity
if any(relative_humidity.data.ravel() < 0) or any(
relative_humidity.data.ravel() > 100):
raise ValueError('heat_index: invalid values for relative humidity')
# Check if relative humidity fractional
if all(relative_humidity.data.ravel() < 1):
warnings.warn(
"WARNING: rh must be %, not fractional; All rh are < 1")
# call internal computation function
heatindex, eqtype = _xheat_index(temperature, relative_humidity,
alternate_coeffs)
# set xarray attributes
heatindex.attrs['long_name'] = "heat index: NWS"
heatindex.attrs['units'] = "F"
heatindex.attrs[
'www'] = "https://www.wpc.ncep.noaa.gov/html/heatindex_equation.shtml"
heatindex.attrs['info'] = "appropriate for shady locations with no wind"
if eqtype == 1:
heatindex.attrs[
'tag'] = "NCL: heat_index_nws; (Steadman+t)*0.5 and Rothfusz"
else:
heatindex.attrs['tag'] = "NCL: heat_index_nws; (Steadman+t)*0.5"
else:
# ensure in numpy array for function call
temperature = np.atleast_1d(temperature)
relative_humidity = np.atleast_1d(relative_humidity)
# input validation on relative humidity
if any(relative_humidity.ravel() < 0) or any(
relative_humidity.ravel() > 100):
raise ValueError('heat_index: invalid values for relative humidity')
# Check if relative humidity fractional
if all(relative_humidity.ravel() < 1):
warnings.warn(
"WARNING: rh must be %, not fractional; All rh are < 1")
# function call for non-dask/xarray
heatindex = _heat_index(temperature, relative_humidity,
alternate_coeffs)
return heatindex
def relhum(
temperature: typing.Union[np.ndarray, xr.DataArray, list, float],
mixing_ratio: typing.Union[np.ndarray, xr.DataArray, list, float],
pressure: typing.Union[np.ndarray, xr.DataArray, list, float]
) -> typing.Union[np.ndarray, xr.DataArray]:
"""This function calculates the relative humidity given temperature, mixing
ratio, and pressure.
"Improved Magnus' Form Approx. of Saturation Vapor pressure"
Oleg A. Alduchov and Robert E. Eskridge
https://journals.ametsoc.org/view/journals/apme/35/4/1520-0450_1996_035_0601_imfaos_2_0_co_2.xml
Parameters
----------
temperature : ndarray, :class:`xarray.DataArray`, :obj:`list`, or :obj:`float`
Temperature in Kelvin
mixing_ratio : ndarray, :class:`xarray.DataArray`, :obj:`list`, or :obj:`float`
Mixing ratio in kg/kg. Must have the same dimensions as ``temperature``
pressure : ndarray, :class:`xarray.DataArray`, :obj:`list`, or :obj:`float`
Pressure in Pa. Must have the same dimensions as ``temperature``
Returns
-------
relative_humidity : ndarray or :class:`xarray.DataArray`
Relative humidity. Will have the same dimensions as ``temperature``
See Also
--------
Related GeoCAT Functions:
:func:`_xrelhum`
:func:`relhum_ice`
:func:`relhum_water`
Related NCL Functions:
`relhum <https://www.ncl.ucar.edu/Document/Functions/Built-in/relhum.shtml>`__,
`relhum_ttd <https://www.ncl.ucar.edu/Document/Functions/Contributed/relhum_ttd.shtml>`__,
`relhum_ice <https://www.ncl.ucar.edu/Document/Functions/Built-in/relhum_ice.shtml>`__,
`relhum_water <https://www.ncl.ucar.edu/Document/Functions/Built-in/relhum_water.shtml>`__
"""
inputs = [temperature, mixing_ratio, pressure]
# ensure all inputs same size
if not (np.shape(x) == np.shape(inputs[0]) for x in inputs):
raise ValueError("relhum: dimensions of inputs are not the same")
# Get input types
in_types = [type(item) for item in inputs]
# run dask compatible version if input is xarray
if xr.DataArray in in_types:
# check all inputs are xarray.DataArray
if not all(x == xr.DataArray for x in in_types):
raise TypeError(
"relhum: if using xarray, all inputs must be xarray")
# call internal computation function
relative_humidity = _xrelhum(temperature, mixing_ratio, pressure)
# set xarray attributes
relative_humidity.attrs['long_name'] = "relative humidity"
relative_humidity.attrs['units'] = 'percentage'
relative_humidity.attrs[
'info'] = 'https://journals.ametsoc.org/view/journals/apme/35/4/1520-0450_1996_035_0601_imfaos_2_0_co_2.xml'
else:
# ensure in numpy array for function call
temperature = np.asarray(temperature)
mixing_ratio = np.asarray(mixing_ratio)
pressure = np.asarray(pressure)
# function call for non-dask/xarray
relative_humidity = _relhum(temperature, mixing_ratio, pressure)
return relative_humidity
def relhum_ice(temperature: typing.Union[np.ndarray, list, float],
mixing_ratio: typing.Union[np.ndarray, list, float],
pressure: typing.Union[np.ndarray, list, float]) -> np.ndarray:
"""Calculates relative humidity with respect to ice, given temperature,
mixing ratio, and pressure.
"Improved Magnus' Form Approx. of Saturation Vapor pressure"
Oleg A. Alduchov and Robert E. Eskridge
https://journals.ametsoc.org/view/journals/apme/35/4/1520-0450_1996_035_0601_imfaos_2_0_co_2.xml
Parameters
----------
temperature : ndarray, :obj:`list`, or :obj:`float`
Temperature in Kelvin
mixing_ratio : ndarray, :obj:`list`, or :obj:`float`
Mixing ratio in kg/kg. Must have the same dimensions as ``temperature``
pressure : ndarray, :obj:`list`, or :obj:`float`
Pressure in Pa. Must have the same dimensions as ``temperature``
Returns
-------
relative_humidity : ndarray
Relative humidity. Will have the same dimensions as ``temperature``
See Also
--------
Related GeoCAT Functions:
:func:`relhum`
:func:`_xrelhum`
:func:`relhum_water`
:func:`_relhum_ice`
Related NCL Functions:
`relhum <https://www.ncl.ucar.edu/Document/Functions/Built-in/relhum.shtml>`__,
`relhum_ttd <https://www.ncl.ucar.edu/Document/Functions/Contributed/relhum_ttd.shtml>`__,
`relhum_ice <https://www.ncl.ucar.edu/Document/Functions/Built-in/relhum_ice.shtml>`__,
`relhum_water <https://www.ncl.ucar.edu/Document/Functions/Built-in/relhum_water.shtml>`__
"""
# If xarray input, pull data and store metadata
x_out = False
if isinstance(temperature, xr.DataArray):
x_out = True
save_dims = temperature.dims
save_coords = temperature.coords
save_attrs = temperature.attrs
# ensure in numpy array for function call
temperature = np.asarray(temperature)
mixing_ratio = np.asarray(mixing_ratio)
pressure = np.asarray(pressure)
# ensure all inputs same size
if np.shape(temperature) != np.shape(mixing_ratio) or np.shape(
temperature) != np.shape(pressure):
raise ValueError(f"relhum_ice: dimensions of inputs are not the same")
relative_humidity = _relhum_ice(temperature, mixing_ratio, pressure)
# output as xarray if input as xarray
if x_out:
relative_humidity = xr.DataArray(data=relative_humidity,
coords=save_coords,
dims=save_dims,
attrs=save_attrs)
return relative_humidity
def relhum_water(temperature: typing.Union[np.ndarray, list, float],
mixing_ratio: typing.Union[np.ndarray, list, float],
pressure: typing.Union[np.ndarray, list, float]) -> np.ndarray:
"""Calculates relative humidity with respect to water, given temperature,
mixing ratio, and pressure.
Definition of mixing ratio if:
- `es` - is the saturation mixing ratio
- `ep` - is the ratio of the molecular weights of water vapor to dry air
- `p` - is the atmospheric pressure
- `rh` - is the relative humidity (given as a percent)
.. math::
rh = 100 q / ( (ep*es)/(p-es) )
Parameters
----------
temperature : ndarray, :obj:`list`, or :obj:`float`
Temperature in Kelvin
mixing_ratio : ndarray, :obj:`list`, or :obj:`float`
Mixing ratio in kg/kg. Must have the same dimensions as ``temperature``
pressure : ndarray, :obj:`list`, or :obj:`float`
Pressure in Pa. Must have the same dimensions as ``temperature``
Returns
-------
relative_humidity : ndarray
Relative humidity. Will have the same dimensions as ``temperature``
See Also
--------
Related GeoCAT Functions:
:func:`relhum`
:func:`_xrelhum`
:func:`relhum_ice`
:func:`relhum_water`
Related NCL Functions:
`relhum <https://www.ncl.ucar.edu/Document/Functions/Built-in/relhum.shtml>`__,
`relhum_ttd <https://www.ncl.ucar.edu/Document/Functions/Contributed/relhum_ttd.shtml>`__,
`relhum_ice <https://www.ncl.ucar.edu/Document/Functions/Built-in/relhum_ice.shtml>`__,
`relhum_water <https://www.ncl.ucar.edu/Document/Functions/Built-in/relhum_water.shtml>`__
"""
# If xarray input, pull data and store metadata
x_out = False
if isinstance(temperature, xr.DataArray):
x_out = True
save_dims = temperature.dims
save_coords = temperature.coords
save_attrs = temperature.attrs
# ensure in numpy array for function call
temperature = np.asarray(temperature)
mixing_ratio = np.asarray(mixing_ratio)
pressure = np.asarray(pressure)
# ensure all inputs same size
if np.shape(temperature) != np.shape(mixing_ratio) or np.shape(
temperature) != np.shape(pressure):
raise ValueError(f"relhum_water: dimensions of inputs are not the same")
relative_humidity = _relhum_water(temperature, mixing_ratio, pressure)
# output as xarray if input as xarray
if x_out:
relative_humidity = xr.DataArray(data=relative_humidity,
coords=save_coords,
dims=save_dims,
attrs=save_attrs)
return relative_humidity
def max_daylight(
jday: typing.Union[np.ndarray, xr.DataArray, list,
float], lat: typing.Union[np.ndarray, xr.DataArray, list,
float]
) -> typing.Union[np.ndarray, xr.DataArray, float]: