Fix warnings issued from successive convert_units_to calls (#1319)

### What kind of change does this PR introduce?

* Fixes a bug in the logic of two indices (`snowfall_approximation` with
`method="brown"`, `effective_growing_degree_days`) that was emitting
usage warnings from valid calls.
* prepends `v` to entries in CHANGES.rst to properly generate hyperlink
entries.
* Warnings from set ``_version_deprecated`` within Indicators now emit
`FutureWarning` instead of `DeprecationWarning` for greater visibility.

### Does this PR introduce a breaking change?

No.

### Other information:

See also: #1010

CHANGES.rst

@@ -2,8 +2,8 @@
 Changelog
 =========
 
-0.42.0 (unreleased)
--------------------
+v0.42.0 (unreleased)
+--------------------
 Contributors to this version: Trevor James Smith (:user:`Zeitsperre`).
 
 New features and enhancements
@@ -13,6 +13,10 @@ New features and enhancements
     * ``xclim.core.calendar.yearly_random_doy``
 * `scipy` is no longer pinned below v1.9 and `lmoments3>=1.0.5` is now a core dependency and installed by default with `pip`. (:issue:`1142`, :pull:`1171`).
 
+Bug fixes
+^^^^^^^^^
+* Warnings emitted from regular usage of some indices (``snowfall_approximation`` with ``method="brown"``, ``effective_growing_degree_days``) due to successive ``convert_units_to`` calls within their logic have been silenced. (:pull:`1319`).
+
 Breaking changes
 ^^^^^^^^^^^^^^^^
 * The call signatures for ``xclim.ensembles.create_ensemble`` and ``xclim.ensembles._base._ens_align_dataset`` have been deprecated. Calls to these functions made with the original signature will emit warnings. Changes will become breaking in `xclim>=0.43.0`.(:issue:`1305`, :pull:`1317`). Affected variable:
@@ -39,9 +43,10 @@ Internal changes
 * Addressed a formatting bug that caused `Indicators` with multiple variables returned to not be properly formatted in the documentation. (:issue:`1305`, :pull:`1317`).
 * `tox` now include `sbck` and `eofs` flags for easier testing of dependencies. CI builds now test against `sbck-python` @ master.  (:pull:`1328`).
 * `upstream` CI tests are now run on push to master, at midnight, and can also be triggered via `workflow_dispatch`. Failures from upstream build will open issues using `xarray-contrib/issue-from-pytest-log`. (:pull:`1327`).
+* Warnings from set ``_version_deprecated`` within Indicators now emit ``FutureWarning`` instead of ``DeprecationWarning`` for greater visibility. (:pull:`1319`).
 
-0.41.0 (2023-02-28)
--------------------
+v0.41.0 (2023-02-28)
+--------------------
 Contributors to this version: Trevor James Smith (:user:`Zeitsperre`), Pascal Bourgault (:user:`aulemahal`), Ludwig Lierhammer (:user:`ludwiglierhammer`), Éric Dupuis (:user:`coxipi`).
 
 New features and enhancements
@@ -94,8 +99,8 @@ Internal changes
 * Added `sphinxcontrib-svg2pdfconverter` for converting SVG graphics within documentation to PDF-compatible images. (:pull:`1296`).
 * README badges for supported Python versions and repository health have been added. (:issue:`1304`, :pull:`1307`).
 
-0.40.0 (2023-01-13)
--------------------
+v0.40.0 (2023-01-13)
+--------------------
 Contributors to this version: Trevor James Smith (:user:`Zeitsperre`), Pascal Bourgault (:user:`aulemahal`), David Huard (:user:`huard`), Juliette Lavoie (:user:`juliettelavoie`).
 
 New features and enhancements
@@ -150,8 +155,8 @@ Internal changes
 * A notebook (``extendingxclim.ipynb``) has been updated to remove mentions of obsolete `xclim.subset` module. (:pull:`1258`).
 * Merge of sdba documentation from the module and the rst files, some cleanup and addition of a section referring to GitHub issues. (:pull:`1230`).
 
-0.39.0 (2022-11-02)
--------------------
+v0.39.0 (2022-11-02)
+--------------------
 Contributors to this version: Trevor James Smith (:user:`Zeitsperre`), Abel Aoun (:user:`bzah`), Éric Dupuis (:user:`coxipi`), Travis Logan (:user:`tlogan2000`), Pascal Bourgault (:user:`aulemahal`).
 
 New features and enhancements
@@ -213,8 +218,8 @@ Internal changes
 * ``show_versions`` can now accept a list of dependencies so that other libraries can make use of this utility. (:pull:`1215`).
 * Pull Requests now are automatically tagged (``CI``, ``docs``, ``indicators``, and/or ``sdba``) according to files modified using the `GitHub Labeler Action <https://github.com/actions/labeler>`_. (:pull:`1214`).
 
-0.38.0 (2022-09-06)
--------------------
+v0.38.0 (2022-09-06)
+--------------------
 Contributors to this version: Pascal Bourgault (:user:`aulemahal`), Éric Dupuis (:user:`coxipi`), Trevor James Smith (:user:`Zeitsperre`), Abel Aoun (:user:`bzah`), Gabriel Rondeau-Genesse (:user:`RondeauG`), Dougie Squire (:user:`dougiesquire`).
 
 New features and enhancements
@@ -287,8 +292,8 @@ Internal changes
 * Adjusted the ANUCLIM indices by removing "ANUCLIM" from their titles, modifying their docstrings, and handling `"op"` input in a more user-friendly way. (:issue:`1055`, :pull:`1169`).
 * Documentation for fire-based indices/indicators has been reorganized to reflect the new submodule structure. (:pull:`1159`).
 
-0.37.0 (2022-06-20)
--------------------
+v0.37.0 (2022-06-20)
+--------------------
 Contributors to this version: Abel Aoun (:user:`bzah`), Pascal Bourgault (:user:`aulemahal`), Trevor James Smith (:user:`Zeitsperre`), Gabriel Rondeau-Genesse (:user:`RondeauG`), Juliette Lavoie (:user:`juliettelavoie`), Ludwig Lierhammer (:user:`ludwiglierhammer`).
 
 Announcements

xclim/core/indicator.py

@@ -1350,9 +1350,10 @@ def injected_parameters(self):
 
     def _show_deprecation_warning(self):
         warnings.warn(
-            f"`{self.title}` is deprecated as of xclim v{self._version_deprecated}. "
-            f"See the xclim release notes for more information.",
-            DeprecationWarning,
+            f"`{self.title}` is deprecated as of `xclim` v{self._version_deprecated} and will be removed "
+            "in a future release. See the `xclim` release notes for more information: "
+            f"https://xclim.readthedocs.io/en/stable/history.html",
+            FutureWarning,
             stacklevel=3,
         )
 

xclim/indices/_agro.py

@@ -1332,17 +1332,20 @@ def effective_growing_degree_days(
     tasmax = convert_units_to(tasmax, "degC")
     tasmin = convert_units_to(tasmin, "degC")
     thresh = convert_units_to(thresh, "degC")
+    thresh_with_units = f"{thresh} degC"
 
     tas = (tasmin + tasmax) / 2
     tas.attrs["units"] = "degC"
 
     if method.lower() == "bootsma":
-        fda = first_day_temperature_above(tas=tas, thresh=thresh, window=1, freq=freq)
+        fda = first_day_temperature_above(
+            tas=tas, thresh=thresh_with_units, window=1, freq=freq
+        )
         start = fda + 10
     elif method.lower() == "qian":
         tas_weighted = qian_weighted_mean_average(tas=tas, dim=dim)
         start = first_day_temperature_above(
-            tas_weighted, thresh=thresh, window=5, freq=freq
+            tas_weighted, thresh=thresh_with_units, window=5, freq=freq
         )
     else:
         raise NotImplementedError(f"Method: {method}.")

xclim/indices/_conversion.py

@@ -819,7 +819,8 @@ def snowfall_approximation(
             raise ValueError("Non-scalar `thresh` are not allowed with method `brown`.")
 
         # Freezing point + 2C in the native units
-        upper = convert_units_to(convert_units_to(thresh, "degC") + 2, tas)
+        thresh_plus_2 = convert_units_to(thresh, "degC") + 2
+        upper = convert_units_to(f"{thresh_plus_2} degC", tas)
         thresh = convert_units_to(thresh, tas)
 
         # Interpolate fraction over temperature (in units of tas)