Fix calc module for dewpoint calculations

metobscommon/util/calc.py

@@ -40,7 +40,7 @@ def dewpoint(tempC, relhum):
 
     if pd is not None and isinstance(dp, pd.Series):
         return pd.concat([dp - 273.15, tempC], axis=1).min(axis=1)
-    return np.min(dp - 273.15, tempC)
+    return np.min([dp - 273.15, tempC])
 
 
 def relhum(airTempK, dewpointTempK):
@@ -51,7 +51,7 @@ def relhum(airTempK, dewpointTempK):
     :param airTempK: air temperature in Kelvin
     :param dewpointTempK: dewpoint temp in Kelvin
     """
-    if airTempK == None or dewpointTempK == None:
+    if airTempK is None or dewpointTempK is None:
         return np.nan
 
     gas_constant = 461.5
@@ -71,7 +71,7 @@ def potentialtemp(airTempK, pressureMB):
     :param airTempK: air temperature in Kelvin
     :param pressureMB: air pressure in millibars
     """
-    if airTempK == None or pressureMB == None:
+    if airTempK is None or pressureMB is None:
         return np.nan
 
     pT = airTempK * (pressureMB.max() / pressureMB) ** .286