add spectra and spectra_components to nomenclature page (#2264)

* Update variables_style_rules.csv

* Update v0.11.2.rst

* not sure what happened here after merge with main

* Update v0.11.2.rst

* update whatsnew and glossary page

* Update spectrl2.py

* Update irradiance.py

* typo

* update spectrl2.py and spectrum irradiance.py

* grammar -- periods before/after units(?)

* Apply suggestions from code review

Co-authored-by: Kevin Anderson <kevin.anderso@gmail.com>

* Update v0.11.2.rst

* fix whatsnew formatting

* formatting attempt #2

---------

Co-authored-by: Kevin Anderson <kevin.anderso@gmail.com>

docs/sphinx/source/user_guide/nomenclature.rst

@@ -142,6 +142,13 @@ There is a convention on consistent variable names throughout the library:
     solar_zenith
         Zenith angle of the sun in degrees
 
+    spectra
+    spectra_components
+        Spectral irradiance (components) [Wm⁻²nm⁻¹]. The amount of energy
+        incident on a unit area per unit time and per unit
+        wavelength. As with broadband irradiance, global spectral irradiance
+        is composed of direct and diffuse components.
+
     surface_azimuth
         Azimuth angle of the surface
 

docs/sphinx/source/whatsnew/v0.11.2.rst

@@ -33,6 +33,10 @@ Documentation
   page, using the sphinx glossary directive. (:issue:`1421`, :pull:`2234`)
 * Explained how to write docstrings for new functions in :ref:`example-docstring`
   (:discussion:`2081`, :pull:`2254`)
+* Added the following variables to the :ref:`nomenclature` page:
+
+  - `spectra` and `spectra_components` (:issue:`2150`, :pull:`2264`)
+
 
 Testing
 ~~~~~~~

pvlib/spectrum/irradiance.py

@@ -189,7 +189,8 @@ def average_photon_energy(spectra):
     ----------
     spectra : pandas.Series or pandas.DataFrame
 
-        Spectral irradiance, must be positive. [Wm⁻²nm⁻¹]
+        Spectral irradiance, must be positive [Wm⁻²nm⁻¹].
+        See :term:`spectra`.
 
         A single spectrum must be a :py:class:`pandas.Series` with wavelength
         [nm] as the index, while multiple spectra must be rows in a

pvlib/spectrum/spectrl2.py

@@ -228,10 +228,11 @@ def spectrl2(apparent_zenith, aoi, surface_tilt, ground_albedo,
     Returns
     -------
     spectra_components : dict
-        A dict of arrays.  With the exception of `wavelength`, which has length
+        A dict of arrays. With the exception of `wavelength`, which has length
         122, each array has shape (122, N) where N is the length of the
         input ``apparent_zenith``.  All values are spectral irradiance
         with units Wm⁻²nm⁻¹, except for `wavelength`, which is in nanometers.
+        See :term:`spectra_components`.
 
         * wavelength
         * dni_extra