Adding Dewpoint Depression and Wetbulb Formulas
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rich T
Nov 1, 2020, 3:58:51 PM11/1/20
to weewx-development
I want to add Dewpoint Depression and Wetbulb Formulas to the wxformulas.py file. So far this is what I have
Does the coding look okay? I know I need to add two columns to the database, but what else would need to be updated to get the results in the database?
Dewpoint Depression:
def dewpointdepressF(t_F, rh):
"""Calculate dew point depression.
t_f: Temperature in Fahrenheit rh: relative humidity [0-100] Returns: Dewpoint Depression """
if t_f is None or rh is None: return None dp_F = dewpointF(t_F, rh) dp_D = t_F - dp_F
return dp_D if dp_D is not None else None
def dewpointdepressC(t_C, rh):
"""Calculate dew point depression.
t_C: temperature in degree Celsius rh: relative humidity [0-100] Returns: Dewpoint Depression """
if t_C is None or rh is None: return None dp_C = dewpointC(t_C, rh) dp_D = t_C - dp_C
return dp_D if dp_D is not None else NoneWetbulb:
def wetbulbF(t_F, rh): """Estimate the wetbulb temperature (1/3 method).
t_f: Temperature in Fahrenheit rh: relative humidity [0-100] dp_DwB: Dewpoint Depression divided by 3 t_WbF: Wetbulb Temperature in Fahrenheit Returns: Wetbulb Temperature Estimation
"""
if t_f is None or rh is None: return None dp_F = dewpointF(t_F, rh) dp_DwB = (t_F - dp_F) / 3 t_WbF = t_F - dp_DwB
return t_WbF if t_WbF is not None else None
def wetbulbC(t_C, rh): """Estimate the wetbulb temperature (1/3 method).
t_C: temperature in degree Celsius rh: relative humidity [0-100] dp_DwB: Dewpoint Depression divided by 3 t_WbC: Wetbulb Temperature in Celsius Returns: Wetbulb Temperature Estimation
"""
if t_C is None or rh is None: return None dp_C = dewpointC(t_C, rh) dp_DwB = (t_C - dp_C) / 3 t_WbC = t_C - dp_DwB
return t_WbC if t_WbC is not None else NoneDoes the coding look okay? I know I need to add two columns to the database, but what else would need to be updated to get the results in the database?
Rich
Tom Keffer
Nov 2, 2020, 7:44:03 AM11/2/20
to rich T, weewx-development
A problem is that you're doing arithmetic before checking for a "None" result. For example,
...
dp_F = dewpointF(t_F, rh)
dp_D = t_F - dp_F
return dp_D if dp_D is not None else None
dp_D = t_F - dp_F
return dp_D if dp_D is not None else None
If db_F is None, this will fail. Same problem with the other algorithms.
As for adding the results to the database, if you add the types through the xtypes system, they will become available throughout WeeWX. Follow the example in the Wiki. The biggest challenge will be checking that the units are right.
-tk
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rich T
Nov 2, 2020, 4:34:31 PM11/2/20
to weewx-development
Thanks Tom. Will give it a try.
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