Fix _m_to_cm: multiply by 100 to convert meters to cm (#2725)

* Fix _m_to_cm: multiply by 100 to convert meters to cm

* Apply suggestion from @cwhanse

Co-authored-by: Cliff Hansen <cwhanse@sandia.gov>

* Docs: document _m_to_cm conversion fix in changelog

* Update tests/iotools/test_era5.py

Co-authored-by: Rajiv Daxini <143435106+RDaxini@users.noreply.github.com>

* Apply suggestion from @RDaxini

Co-authored-by: Rajiv Daxini <143435106+RDaxini@users.noreply.github.com>

---------

Co-authored-by: JB <jbpasquier@ombrea.fr>
Co-authored-by: Cliff Hansen <cwhanse@sandia.gov>
Co-authored-by: Rajiv Daxini <143435106+RDaxini@users.noreply.github.com>

Author: 4 people

docs/sphinx/source/whatsnew/v0.15.1.rst

@@ -20,6 +20,10 @@ Bug fixes
 * Fix a division-by-zero condition in
   :py:func:`pvlib.transformer.simple_efficiency` when ``load_loss = 0``.
   (:issue:`2645`, :pull:`2646`)
+* Fix a bug in :py:func:`pvlib.iotools.era5._m_to_cm` where meters were
+  incorrectly divided by 100 instead of multiplied, causing precipitations to be
+  underestimated by a factor of 10,000 when ``map_variables=True``.
+  (:issue:`2724`, :pull:`2725`)
 
 Enhancements
 ~~~~~~~~~~~~
@@ -79,4 +83,5 @@ Contributors
 * Kevin Anderson (:ghuser:`kandersolar`)
 * Rohan Saxena (:ghuser:`r0hansaxena`)
 * Marco Fumagalli (:ghuser:`fuma900`)
+* Jean-Baptiste Pasquier (:ghuser:`pasquierjb`)
 

pvlib/iotools/era5.py

@@ -37,7 +37,7 @@ def _j_to_w(j):
 
 
 def _m_to_cm(m):
-    return m / 100
+    return m * 100
 
 
 UNITS = {

tests/iotools/test_era5.py

@@ -92,3 +92,8 @@ def test_get_era5_timeout(params):
     match = 'Request timed out. Try increasing'
     with pytest.raises(requests.exceptions.Timeout, match=match):
         df, meta = pvlib.iotools.get_era5(**params, timeout=1)
+
+
+def test__m_to_cm():
+    from pvlib.iotools.era5 import _m_to_cm
+    assert _m_to_cm(0.01) == 1  # 0.01 m = 1 cm