Initial implementation of CAPE calculation

Initial implementation of CAPE calculation; need to fix EL calculation
to achieve valid results

lib/xmet/sounding.py

@@ -9,7 +9,10 @@ from xmet.list   import nearest
 from xmet.series import Series, SeriesIntersection
 from xmet.thermo import follow_dry_adiabat, \
                         follow_moist_adiabat, \
-                        follow_saturated_mixing_ratio
+                        follow_saturated_mixing_ratio, \
+                        pressure_height, \
+                        kelvin, \
+                        celsius
 
 LAPSE_RATE_DRY   = 9.8 # degrees C per 1000m
 LAPSE_RATE_MOIST = 4.0
@@ -184,7 +187,41 @@ class Sounding(DatabaseTable):
 
         return series
 
+def between(n, a, b):
+    return n > a and n < b
+
 class SoundingParameters():
+    @staticmethod
+    def cape(temp_line: Series,
+             moist_adiabat: Series,
+             lfc: tuple[float],
+             el: tuple[float]) -> float:
+        cape = 0.0
+
+        p_lfc, p_el = lfc[1], el[1]
+
+        neighbors = temp_line.neighbors(moist_adiabat)
+        gph_last  = None
+
+        for pair in neighbors:
+            p_env, p_parcel = pair
+
+            if not between(p_env, p_el, p_lfc):
+                continue
+
+            t_env    = kelvin(temp_line[p_env])
+            t_parcel = kelvin(moist_adiabat[p_parcel])
+            gph      = pressure_height(p_env)
+
+            if gph_last is not None:
+                gph_delta = gph - gph_last
+
+                cape += (((t_parcel) - (t_env)) / (t_env)) * gph_delta
+
+            gph_last = gph
+
+        return cape
+
     @staticmethod
     def from_sounding(sounding: Sounding) -> Self:
         temp_line   = sounding.follow_temp()
@@ -202,8 +239,12 @@ class SoundingParameters():
         el  = moist_adiabat.intersect(temp_line, SeriesIntersection.LESSER, lfc[1])
 
         params = SoundingParameters()
-        params.lcl = lcl
+        params.lcl  = lcl
-        params.lfc = lfc
+        params.lfc  = lfc
-        params.el  = el
+        params.el   = el
+        params.cape = SoundingParameters.cape(temp_line,
+                                              moist_adiabat,
+                                              lfc,
+                                              el)
 
         return params