Merge pull request Unidata#1516 from dopplershift/fix-1496

BUG: Fix passing masked arrays to CAPE/CIN calcs

src/metpy/calc/thermo.py

@@ -837,7 +837,7 @@ def _insert_lcl_level(pressure, temperature, lcl_pressure):
     # Pressure needs to be increasing for searchsorted, so flip it and then convert
     # the index back to the original array
     loc = pressure.size - pressure[::-1].searchsorted(lcl_pressure)
-    return np.insert(temperature.m, loc, interp_temp.m) * temperature.units
+    return temperature.units * np.insert(temperature.m, loc, interp_temp.m)
 
 
 @exporter.export
@@ -1720,7 +1720,7 @@ def _find_append_zero_crossings(x, y):
         y values of data
 
     """
-    crossings = find_intersections(x[1:], y[1:], np.zeros_like(y[1:]) * y.units, log_x=True)
+    crossings = find_intersections(x[1:], y[1:], y.units * np.zeros_like(y[1:]), log_x=True)
     x = concatenate((x, crossings[0]))
     y = concatenate((y, crossings[1]))
 

tests/calc/test_thermo.py

@@ -37,7 +37,7 @@
                         wet_bulb_temperature)
 from metpy.calc.thermo import _find_append_zero_crossings
 from metpy.testing import assert_almost_equal, assert_array_almost_equal, assert_nan
-from metpy.units import units
+from metpy.units import masked_array, units
 
 
 def test_relative_humidity_from_dewpoint():
@@ -1159,11 +1159,12 @@ def test_isentropic_interpolation_as_dataset():
     assert result['isentropic_level'].attrs == expected['isentropic_level'].attrs
 
 
-def test_surface_based_cape_cin():
+@pytest.mark.parametrize('array_class', (units.Quantity, masked_array))
+def test_surface_based_cape_cin(array_class):
     """Test the surface-based CAPE and CIN calculation."""
-    p = np.array([959., 779.2, 751.3, 724.3, 700., 269.]) * units.mbar
-    temperature = np.array([22.2, 14.6, 12., 9.4, 7., -38.]) * units.celsius
-    dewpoint = np.array([19., -11.2, -10.8, -10.4, -10., -53.2]) * units.celsius
+    p = array_class([959., 779.2, 751.3, 724.3, 700., 269.], units.mbar)
+    temperature = array_class([22.2, 14.6, 12., 9.4, 7., -38.], units.celsius)
+    dewpoint = array_class([19., -11.2, -10.8, -10.4, -10., -53.2], units.celsius)
     cape, cin = surface_based_cape_cin(p, temperature, dewpoint)
     assert_almost_equal(cape, 75.7340825 * units('joule / kilogram'), 2)
     assert_almost_equal(cin, -136.607809 * units('joule / kilogram'), 2)