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Change refraction correction limit in ephemeris solar position algorithm #2524

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Change refraction correction limit in ephemeris solar position algorithm #2524

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Change refraction correction limit in ephemeris solar position algorithm
AdamRJensen Aug 1, 2025
068b02b
Add testing and whatsnew
AdamRJensen Aug 2, 2025
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3 changes: 3 additions & 0 deletions docs/sphinx/source/whatsnew/v0.13.1.rst
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Expand Up @@ -6,6 +6,9 @@ v0.13.1 (Anticipated September, 2025)

Breaking Changes
~~~~~~~~~~~~~~~~
* Change refraction for solar elevation angles between 85 and 90
degrees to be calculated rather than set to 0 in
:py:func:`~pvlib.solarposition.ephemeris`. (:pull:`2524`)
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I guess this qualifies more like a bugfix rather than a Breaking Change - I don't see how my code would not run after this update.



Deprecations
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2 changes: 1 addition & 1 deletion pvlib/solarposition.py
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Expand Up @@ -828,7 +828,7 @@ def ephemeris(time, latitude, longitude, pressure=101325.0, temperature=12.0):
TanEl = pd.Series(np.tan(np.radians(Elevation)), index=time_utc)
Refract = pd.Series(0., index=time_utc)

Refract[(Elevation > 5) & (Elevation <= 85)] = (
Refract[(Elevation > 5) & (Elevation <= 90)] = (
58.1/TanEl - 0.07/(TanEl**3) + 8.6e-05/(TanEl**5))

Refract[(Elevation > -0.575) & (Elevation <= 5)] = (
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12 changes: 12 additions & 0 deletions tests/test_solarposition.py
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Expand Up @@ -964,3 +964,15 @@ def test_spa_python_numba_physical_dst(expected_solpos, golden):
temperature=11, delta_t=67,
atmos_refract=0.5667,
how='numpy', numthreads=1)


def test_ephmeris_refraction_85_90_degrees():
# Test that refraction is calculated rather than set to zero
# for solar elevatoin angles between 85 and 90 degrees
# PR#2524
# The below example has a solar elevation angle of 87.9
result = solarposition.ephemeris(
time=pd.date_range('2020-03-23 12', periods=1, tz='UTC'),
latitude=0, longitude=0)
refraction = (result['apparent_zenith'] - result['zenith']).iloc[0]
assert refraction == -0.0005818446332597205
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