Better readability

lib/xmet/sounding.py

@@ -13,8 +13,7 @@ from xmet.thermo import follow_dry_adiabat, \
                         pressure_height, \
                         virtual_temp, \
                         kelvin, \
-                        wind_u, \
-                        wind_v
+                        wind_uv
 
 from xmet.units import deg
 
@@ -213,11 +212,17 @@ class Sounding(DatabaseTable):
         s1 = self.samples[level]
         s2 = self.samples[level+1]
 
-        u1 = wind_u(s1.wind_speed, s1.wind_dir)
-        u2 = wind_u(s2.wind_speed, s2.wind_dir)
+        u1, v1 = wind_uv(s1.wind_speed, s1.wind_dir)
+        u2, v2 = wind_uv(s2.wind_speed, s2.wind_dir)
 
-        v1 = wind_v(s1.wind_speed, s1.wind_dir)
-        v2 = wind_v(s2.wind_speed, s2.wind_dir)
+        return abs(u2 - u1), abs(v2 - v1)
+
+    def shear_magnitude(self, level: int):
+        s1 = self.samples[level]
+        s2 = self.samples[level+1]
+
+        u1, v1 = wind_uv(s1.wind_speed, s1.wind_dir)
+        u2, v2 = wind_uv(s2.wind_speed, s2.wind_dir)
 
         zd = s2.height - s1.height
 
@@ -232,18 +237,18 @@ class Sounding(DatabaseTable):
     def bulk_shear(self):
         levels = len(self.samples) - 1
 
-        shear_speed = 0.0
-        shear_dir   = 0.0
+        shear_u = 0.0
+        shear_v = 0.0
 
         for level in range(0, levels):
             shear = self.shear(level)
 
-            shear_speed += shear[0]
-            shear_dir   += shear[1]
+            shear_u += shear[0]
+            shear_v += shear[1]
 
         return (
-            shear_speed / levels,
-            shear_dir   / levels
+            shear_u / levels,
+            shear_v / levels
         )
 
 def between(n, a, b):

lib/xmet/thermo.py

@@ -5,7 +5,8 @@ from typing import Callable
 from xmet.series import Series
 from xmet.units  import rad, deg, kelvin, celsius
 
-LAPSE_RATE_DRY = 9.8 / 1000 # degrees C per km
+LAPSE_RATE_DRY          = 9.8 / 1000 # degrees C per km
+LAPSE_RATE_MAGIC_FACTOR = 1.09       # adjustment for accuracy
 
 PRESSURE_MAX  = 1050 # millibar
 PRESSURE_MSL  = 1013.25
@@ -130,7 +131,8 @@ def loft_parcel(start_temp: float,
             except OverflowError:
                 break
 
-            temp = lapse(temp, height - last_height, 1.09*rate)
+            temp = lapse(temp, height - last_height,
+                         LAPSE_RATE_MAGIC_FACTOR*rate)
 
             yield temp, pressure
 
@@ -192,10 +194,10 @@ def follow_saturated_mixing_ratio(temp: float, pressure: float, step: float=1.0)
     return series
 
 def wind_u(speed: float, direction: float) -> float:
-    return speed * math.cos(rad(direction))
+    return math.cos(rad(direction)) * speed
 
 def wind_v(speed: float, direction: float) -> float:
-    return -speed * math.sin(rad(direction))
+    return math.sin(rad(direction)) * -speed
 
 def wind_uv(speed: float, direction: float) -> float:
     return (
@@ -206,5 +208,5 @@ def wind_uv(speed: float, direction: float) -> float:
 def wind_speed_dir(u: float, v: float) -> float:
     return (
         math.sqrt(u**2 + v**2),
-        (180 - deg(math.atan2(v, u))) % 360
+        (deg(math.atan2(v, u)) - 180) % 360
     )