fix mlcape if parcel_start_pressure != bottom (#3147)

* fix mlcape if parcel_start_pressure != bottom * fix spacing * split that test
Unidata · Nov 15, 2023 · 64faccb · 64faccb
1 parent eaa93e7
commit 64faccb
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Showing 2 changed files with 13 additions and 3 deletions.
diff --git a/src/metpy/calc/thermo.py b/src/metpy/calc/thermo.py
@@ -3027,13 +3027,14 @@ def mixed_layer_cape_cin(pressure, temperature, dewpoint, **kwargs):
 
     """
     depth = kwargs.get('depth', units.Quantity(100, 'hPa'))
+    start_p = kwargs.get('parcel_start_pressure', pressure[0])
     parcel_pressure, parcel_temp, parcel_dewpoint = mixed_parcel(pressure, temperature,
                                                                  dewpoint, **kwargs)
 
     # Remove values below top of mixed layer and add in the mixed layer values
-    pressure_prof = pressure[pressure < (pressure[0] - depth)]
-    temp_prof = temperature[pressure < (pressure[0] - depth)]
-    dew_prof = dewpoint[pressure < (pressure[0] - depth)]
+    pressure_prof = pressure[pressure < (start_p - depth)]
+    temp_prof = temperature[pressure < (start_p - depth)]
+    dew_prof = dewpoint[pressure < (start_p - depth)]
     pressure_prof = concatenate([parcel_pressure, pressure_prof])
     temp_prof = concatenate([parcel_temp, temp_prof])
     dew_prof = concatenate([parcel_dewpoint, dew_prof])

diff --git a/tests/calc/test_thermo.py b/tests/calc/test_thermo.py
@@ -1556,6 +1556,15 @@ def test_mixed_layer_cape_cin(multiple_intersections):
     assert_almost_equal(mlcin, -13.4809966289 * units('joule / kilogram'), 2)
 
 
+def test_mixed_layer_cape_cin_bottom_pressure(multiple_intersections):
+    """Test the calculation of mixed layer cape/cin with a specified bottom pressure."""
+    pressure, temperature, dewpoint = multiple_intersections
+    mlcape_middle, mlcin_middle = mixed_layer_cape_cin(pressure, temperature, dewpoint,
+                                                       parcel_start_pressure=800 * units.hPa)
+    assert_almost_equal(mlcape_middle, 0 * units('joule / kilogram'), 2)
+    assert_almost_equal(mlcin_middle, 0 * units('joule / kilogram'), 2)
+
+
 def test_dcape():
     """Test the calculation of DCAPE."""
     pressure = [1008., 1000., 950., 900., 850., 800., 750., 700., 650., 600.,