calc.moist_lapse returns incorrect values for Fahrenheit

[joejoezz]

Hello...first time issue reporter here, hopefully I'm doing this right but if not please let me know. It appears that metpy.calc.moist_lapse doesn't work for degrees F, which in turn also causes metpy.calc.wet_bulb_temperature to return wrong values. Here is a test with a temp of 70 F, a dew point of 30 F, and a pressure of 1013 hPa. The wet bulb temperature should be 50.27 degrees F. Thanks!

import metpy.calc as mpcalc
from metpy.units import units

temp_f = 70 * units('degF')
dewpt_f = 30 * units('degF')
pressure = 1013 * units('hPa')
temp_c = temp_f.to('degC')
dewpt_c = dewpt_f.to('degC')

# wet bulb C vs F comparison
wet_bulb_c = mpcalc.wet_bulb_temperature(pressure, temp_c, dewpt_c)
wet_bulb_f = mpcalc.wet_bulb_temperature(pressure, temp_f, dewpt_f)
print('Wet bulb test')
print(wet_bulb_c.to('degF'))
print(wet_bulb_f)

# LCL C vs F comparison
lcl_press_c, lcl_temp_c = mpcalc.lcl(pressure, temp_c, dewpt_c)
lcl_press_f, lcl_temp_f = mpcalc.lcl(pressure, temp_f, dewpt_f)
print('LCL test')
print(lcl_temp_c.to('degF'))
print(lcl_temp_f)

# moist lapse C vs F comparison
t_sfc_f = mpcalc.moist_lapse(pressure, lcl_temp_f, lcl_press_f)
t_sfc_c = mpcalc.moist_lapse(pressure, lcl_temp_c, lcl_press_c)
print('Moist lapse test')
print(t_sfc_c.to('degF'))
print(t_sfc_f)

And the output...
Wet bulb test
50.27419018728051 degree_Fahrenheit
38.64463846517734 degree_Fahrenheit
LCL test
21.973671886917185 degree_Fahrenheit
21.973671886917185 degree_Fahrenheit
Moist lapse test
50.27419018728051 degree_Fahrenheit
38.64463846517734 degree_Fahrenheit

Python 3.6.13, Metpy 1.0.1

[dopplershift]

Thanks for the report, and all of the detailed information above. You definitely found a corner case in our unit-handling. Testing and fixing this also revealed a direct problem in the unit-handling in wet_bulb_temperature itself too. The fix will be included in the forthcoming 1.1 release.