Merge pull request #1426 from jthielen/fix-1364-2

 Fix masked array issue in equivalent potential temperature

src/metpy/calc/thermo.py

@@ -988,7 +988,7 @@ def equivalent_potential_temperature(pressure, temperature, dewpoint):
     th_l = t * (1000 / (p - e)) ** mpconsts.kappa * (t / t_l) ** (0.28 * r)
     th_e = th_l * np.exp((3036. / t_l - 1.78) * r * (1 + 0.448 * r))
 
-    return th_e * units.kelvin
+    return units.Quantity(th_e, units.kelvin)
 
 
 @exporter.export
@@ -1055,7 +1055,7 @@ def saturation_equivalent_potential_temperature(pressure, temperature):
     th_l = t * (1000 / (p - e)) ** mpconsts.kappa
     th_es = th_l * np.exp((3036. / t - 1.78) * r * (1 + 0.448 * r))
 
-    return th_es * units.kelvin
+    return units.Quantity(th_es, units.kelvin)
 
 
 @exporter.export

tests/calc/test_thermo.py

@@ -476,6 +476,24 @@ def test_equivalent_potential_temperature():
     assert_almost_equal(ept, 311.18586467284007 * units.kelvin, 3)
 
 
+def test_equivalent_potential_temperature_masked():
+    """Test equivalent potential temperature calculation with masked arrays."""
+    p = 1000 * units.mbar
+    t = units.Quantity(np.ma.array([293., 294., 295.]), units.kelvin)
+    td = units.Quantity(
+        np.ma.array([280., 281., 282.], mask=[False, True, False]),
+        units.kelvin
+    )
+    ept = equivalent_potential_temperature(p, t, td)
+    expected = units.Quantity(
+        np.ma.array([311.18586, 313.51781, 315.93971], mask=[False, True, False]),
+        units.kelvin
+    )
+    assert isinstance(ept, units.Quantity)
+    assert isinstance(ept.m, np.ma.MaskedArray)
+    assert_array_almost_equal(ept, expected, 3)
+
+
 def test_saturation_equivalent_potential_temperature():
     """Test saturation equivalent potential temperature calculation."""
     p = 700 * units.mbar
@@ -486,6 +504,20 @@ def test_saturation_equivalent_potential_temperature():
     assert_almost_equal(s_ept, 299.096584 * units.kelvin, 3)
 
 
+def test_saturation_equivalent_potential_temperature_masked():
+    """Test saturation equivalent potential temperature calculation with masked arrays."""
+    p = 1000 * units.mbar
+    t = units.Quantity(np.ma.array([293., 294., 295.]), units.kelvin)
+    s_ept = saturation_equivalent_potential_temperature(p, t)
+    expected = units.Quantity(
+        np.ma.array([335.02750, 338.95813, 343.08740]),
+        units.kelvin
+    )
+    assert isinstance(s_ept, units.Quantity)
+    assert isinstance(s_ept.m, np.ma.MaskedArray)
+    assert_array_almost_equal(s_ept, expected, 3)
+
+
 def test_virtual_temperature():
     """Test virtual temperature calculation."""
     t = 288. * units.kelvin