Limit shading of CIN

examples/Advanced_Sounding.py

@@ -73,7 +73,7 @@
 skew.plot(p, prof, 'k', linewidth=2)
 
 # Shade areas of CAPE and CIN
-skew.shade_cin(p, T, prof)
+skew.shade_cin(p, T, prof, Td)
 skew.shade_cape(p, T, prof)
 
 # An example of a slanted line at constant T -- in this case the 0

src/metpy/plots/skewt.py

@@ -23,7 +23,7 @@
 import numpy as np
 
 from ._util import colored_line
-from ..calc import dewpoint, dry_lapse, moist_lapse, vapor_pressure
+from ..calc import dewpoint, dry_lapse, el, lcl, moist_lapse, vapor_pressure
 from ..calc.tools import _delete_masked_points
 from ..deprecation import metpyDeprecation
 from ..interpolate import interpolate_1d
@@ -666,7 +666,7 @@ def shade_area(self, y, x1, x2=0, which='both', **kwargs):
         return self.ax.fill_betweenx(*arrs, **fill_args)
 
     def shade_cape(self, p, t, t_parcel, **kwargs):
-        r"""Shade areas of CAPE.
+        r"""Shade areas of Convective Available Potential Energy (CAPE).
 
         Shades areas where the parcel is warmer than the environment (areas of positive
         buoyancy.
@@ -677,8 +677,12 @@ def shade_cape(self, p, t, t_parcel, **kwargs):
             Pressure values
         t : array_like
             Temperature values
+        dewpoint : array_like
+            Dewpoint values
         t_parcel : array_like
             Parcel path temperature values
+        limit_shading : bool
+            Eliminate shading below the LCL or above the EL, default is True
         kwargs
             Other keyword arguments to pass to :class:`matplotlib.collections.PolyCollection`
 
@@ -694,11 +698,12 @@ def shade_cape(self, p, t, t_parcel, **kwargs):
         """
         return self.shade_area(p, t_parcel, t, which='positive', **kwargs)
 
-    def shade_cin(self, p, t, t_parcel, **kwargs):
-        r"""Shade areas of CIN.
+    def shade_cin(self, p, t, t_parcel, dewpoint=None, **kwargs):
+        r"""Shade areas of Convective INhibition (CIN).
 
         Shades areas where the parcel is cooler than the environment (areas of negative
-        buoyancy.
+        buoyancy. If `dewpoint` is passed in, negative area below the lifting condensation
+        level or above the equilibrium level is not shaded.
 
         Parameters
         ----------
@@ -708,6 +713,8 @@ def shade_cin(self, p, t, t_parcel, **kwargs):
             Temperature values
         t_parcel : array_like
             Parcel path temperature values
+        dewpoint : array_like
+            Dew point values, optional
         kwargs
             Other keyword arguments to pass to :class:`matplotlib.collections.PolyCollection`
 
@@ -721,7 +728,13 @@ def shade_cin(self, p, t, t_parcel, **kwargs):
         :func:`matplotlib.axes.Axes.fill_betweenx`
 
         """
-        return self.shade_area(p, t_parcel, t, which='negative', **kwargs)
+        if dewpoint is not None:
+            lcl_p, _ = lcl(p[0], t[0], dewpoint[0])
+            el_p, _ = el(p, t, dewpoint, t_parcel)
+            idx = np.logical_and(p > el_p, p < lcl_p)
+        else:
+            idx = np.arange(0, len(p))
+        return self.shade_area(p[idx], t_parcel[idx], t[idx], which='negative', **kwargs)
 
 
 @exporter.export

tests/plots/test_skewt.py

@@ -147,31 +147,73 @@ def test_skewt_units():
 @pytest.fixture()
 def test_profile():
     """Return data for a test profile."""
-    return np.linspace(1000, 100, 10), np.linspace(20, -20, 10), np.linspace(25, -30, 10)
-
-
-@pytest.mark.mpl_image_compare(tolerance=.02, remove_text=True, style='default')
+    pressure = np.array([966., 937.2, 925., 904.6, 872.6, 853., 850., 836., 821., 811.6, 782.3,
+                         754.2, 726.9, 700., 648.9, 624.6, 601.1, 595., 587., 576., 555.7,
+                         534.2, 524., 500., 473.3, 400., 384.5, 358., 343., 308.3, 300., 276.,
+                         273., 268.5, 250., 244.2, 233., 200.]) * units.mbar
+    temperature = np.array([18.2, 16.8, 16.2, 15.1, 13.3, 12.2, 12.4, 14., 14.4,
+                            13.7, 11.4, 9.1, 6.8, 4.4, -1.4, -4.4, -7.3, -8.1,
+                            -7.9, -7.7, -8.7, -9.8, -10.3, -13.5, -17.1, -28.1, -30.7,
+                            -35.3, -37.1, -43.5, -45.1, -49.9, -50.4, -51.1, -54.1, -55.,
+                            -56.7, -57.5]) * units.degC
+    dewpoint = np.array([16.9, 15.9, 15.5, 14.2, 12.1, 10.8, 8.6, 0., -3.6, -4.4,
+                        -6.9, -9.5, -12., -14.6, -15.8, -16.4, -16.9, -17.1, -27.9, -42.7,
+                        -44.1, -45.6, -46.3, -45.5, -47.1, -52.1, -50.4, -47.3, -57.1,
+                        -57.9, -58.1, -60.9, -61.4, -62.1, -65.1, -65.6,
+                        -66.7, -70.5]) * units.degC
+    profile = np. array([18.2, 16.18287437, 15.68644745, 14.8369451,
+                        13.45220646, 12.57020365, 12.43280242, 11.78283506,
+                        11.0698586, 10.61393901, 9.14490966, 7.66233636,
+                        6.1454231, 4.56888673, 1.31644072, -0.36678427,
+                        -2.09120703, -2.55566745, -3.17594616, -4.05032505,
+                        -5.73356001, -7.62361933, -8.56236581, -10.88846868,
+                        -13.69095789, -22.82604468, -25.08463516, -29.26014016,
+                        -31.81335912, -38.29612829, -39.97374452, -45.11966793,
+                        -45.79482793, -46.82129892, -51.21936594, -52.65924319,
+                        -55.52598916, -64.68843697]) * units.degC
+    return pressure, temperature, dewpoint, profile
+
+
+@pytest.mark.mpl_image_compare(tolerance=.033, remove_text=True, style='default')
 def test_skewt_shade_cape_cin(test_profile):
     """Test shading CAPE and CIN on a SkewT plot."""
-    p, t, tp = test_profile
+    p, t, td, tp = test_profile
 
     with matplotlib.rc_context({'axes.autolimit_mode': 'data'}):
         fig = plt.figure(figsize=(9, 9))
         skew = SkewT(fig, aspect='auto')
         skew.plot(p, t, 'r')
         skew.plot(p, tp, 'k')
         skew.shade_cape(p, t, tp)
+        skew.shade_cin(p, t, tp, td)
+        skew.ax.set_xlim(-50, 50)
+        skew.ax.set_ylim(1000, 100)
+
+    return fig
+
+
+@pytest.mark.mpl_image_compare(tolerance=0.033, remove_text=True, style='default')
+def test_skewt_shade_cape_cin_no_limit(test_profile):
+    """Test shading CIN without limits."""
+    p, t, _, tp = test_profile
+
+    with matplotlib.rc_context({'axes.autolimit_mode': 'data'}):
+        fig = plt.figure(figsize=(9, 9))
+        skew = SkewT(fig)
+        skew.plot(p, t, 'r')
+        skew.plot(p, tp, 'k')
+        skew.shade_cape(p, t, tp)
         skew.shade_cin(p, t, tp)
         skew.ax.set_xlim(-50, 50)
         skew.ax.set_ylim(1000, 100)
 
     return fig
 
 
-@pytest.mark.mpl_image_compare(tolerance=0.02, remove_text=True, style='default')
+@pytest.mark.mpl_image_compare(tolerance=0.033, remove_text=True, style='default')
 def test_skewt_shade_area(test_profile):
     """Test shading areas on a SkewT plot."""
-    p, t, tp = test_profile
+    p, t, _, tp = test_profile
 
     with matplotlib.rc_context({'axes.autolimit_mode': 'data'}):
         fig = plt.figure(figsize=(9, 9))
@@ -187,7 +229,7 @@ def test_skewt_shade_area(test_profile):
 
 def test_skewt_shade_area_invalid(test_profile):
     """Test shading areas on a SkewT plot."""
-    p, t, tp = test_profile
+    p, t, _, tp = test_profile
     fig = plt.figure(figsize=(9, 9))
     skew = SkewT(fig, aspect='auto')
     skew.plot(p, t, 'r')
@@ -196,10 +238,10 @@ def test_skewt_shade_area_invalid(test_profile):
         skew.shade_area(p, t, tp, which='positve')
 
 
-@pytest.mark.mpl_image_compare(tolerance=0.02, remove_text=True, style='default')
+@pytest.mark.mpl_image_compare(tolerance=0.033, remove_text=True, style='default')
 def test_skewt_shade_area_kwargs(test_profile):
     """Test shading areas on a SkewT plot with kwargs."""
-    p, t, tp = test_profile
+    p, t, _, tp = test_profile
 
     with matplotlib.rc_context({'axes.autolimit_mode': 'data'}):
         fig = plt.figure(figsize=(9, 9))
@@ -213,10 +255,10 @@ def test_skewt_shade_area_kwargs(test_profile):
     return fig
 
 
-@pytest.mark.mpl_image_compare(tolerance=0, remove_text=True, style='default')
+@pytest.mark.mpl_image_compare(tolerance=0.039, remove_text=True, style='default')
 def test_skewt_wide_aspect_ratio(test_profile):
     """Test plotting a skewT with a wide aspect ratio."""
-    p, t, tp = test_profile
+    p, t, _, tp = test_profile
 
     fig = plt.figure(figsize=(12.5, 3))
     skew = SkewT(fig, aspect='auto')

tutorials/upperair_soundings.py

@@ -139,7 +139,7 @@
 skew.plot(p, parcel_prof, 'k', linewidth=2)
 
 # Shade areas of CAPE and CIN
-skew.shade_cin(p, T, parcel_prof)
+skew.shade_cin(p, T, parcel_prof, Td)
 skew.shade_cape(p, T, parcel_prof)
 
 # Plot a zero degree isotherm
@@ -182,7 +182,7 @@
 skew.plot(p, parcel_prof, 'k', linewidth=2)
 
 # Shade areas of CAPE and CIN
-skew.shade_cin(p, T, parcel_prof)
+skew.shade_cin(p, T, parcel_prof, Td)
 skew.shade_cape(p, T, parcel_prof)
 
 # Plot a zero degree isotherm