Wet Bulb Function 'memoryview' Error

[jsillin]

Hi all,
I am attempting to compute wet bulb temperatures using arrays of pressure, temperature, and dew point that I have extracted from gridded model data:

sound_temps = data['temperature'].interp(lat=soundlat,lon=soundlon)-273.15
sound_rh = data['rh'].interp(lat=soundlat,lon=soundlon)
sound_dp = mpcalc.dewpoint_from_relative_humidity(sound_temps.data*units.degC,sound_rh.data*units.percent)
sound_wb = mpcalc.wet_bulb_temperature(sound_pres.data*units.hPa,sound_temps.data*units.degC,sound_dp.data*units.degC)

temps, rh, and dp all work well but wet bulb gives me the following error:

Traceback (most recent call last):
  File "gfs_hrly_ptype_soundings_wetbulb.py", line 319, in <module>
    sound_wb = mpcalc.wet_bulb_temperature(sound_pres.data*units.hPa,sound_temps.data*units.degC,sound_dp.data*units.degC)
  File "C:\Users\Jack\anaconda3\envs\metpy2\lib\site-packages\pint\unit.py", line 188, in __mul__
    return self._REGISTRY.Quantity(1, self._units) * other
  File "C:\Users\Jack\anaconda3\envs\metpy2\lib\site-packages\pint\quantity.py", line 1250, in __mul__
    return self._mul_div(other, operator.mul)
  File "C:\Users\Jack\anaconda3\envs\metpy2\lib\site-packages\pint\quantity.py", line 115, in wrapped
    return f(self, *args, **kwargs)
  File "C:\Users\Jack\anaconda3\envs\metpy2\lib\site-packages\pint\quantity.py", line 95, in wrapped
    result = f(self, *args, **kwargs)
  File "C:\Users\Jack\anaconda3\envs\metpy2\lib\site-packages\pint\quantity.py", line 1216, in _mul_div
    magnitude = magnitude_op(self._magnitude, other_magnitude)
TypeError: unsupported operand type(s) for *: 'int' and 'memoryview'

Any idea what might be the problem here?

Thanks as always for all the help

[jthielen]

I suspect something weird in xarray is happening (i.e., that .data is not converting its internal memoryview to a loaded ndarray), but am not sure. (EDIT: see below discussion...it looks like this is just sound_dp being a pint Quantity in this case.) Would you be able to list the following?

type(sound_pres.data)
type(sound_temps.data)
type(sound_dp.data)

Also, what happens if you use .values (which forces ndarray) instead of .data (which is just supposed to by ndarray-like)?

[jthielen]

Ah, I didn't see your reply when I updated my comment above. Would you be able to take a look at the suggestions in that edit?

[jsillin]

No worries, I manually set the data and units stuff in the calculation because metpy just wouldn't seem to understand that units existed if I set them earlier. Kept getting the 'requires [temp] but given [dimensionless]' error even when I had sound_temps = sound_temps*units.degC directly above it haha.

When I took all that out and put in

        sound_temps = data['temperature'].interp(lat=soundlat,lon=soundlon)
        sound_rh = data['rh'].interp(lat=soundlat,lon=soundlon)

        sound_temps.attrs['units'] = 'K'
        sound_rh.attrs['units'] = 'percent'

        sound_dp = mpcalc.dewpoint_from_relative_humidity(sound_temps, sound_rh)
        sound_wb = mpcalc.wet_bulb_temperature(sound_pres, sound_temps, sound_dp)

I got a new (to me) error

Traceback (most recent call last):
  File "gfs_hrly_ptype_soundings_wetbulb.py", line 334, in <module>
    sound_wb = mpcalc.wet_bulb_temperature(sound_pres, sound_temps, sound_dp)
  File "C:\Users\Jack\anaconda3\envs\metpy2\lib\site-packages\metpy\xarray.py", line 677, in wrapper
    return func(*args, **kwargs)
  File "C:\Users\Jack\anaconda3\envs\metpy2\lib\site-packages\metpy\units.py", line 320, in wrapper
    return func(*args, **kwargs)
  File "C:\Users\Jack\anaconda3\envs\metpy2\lib\site-packages\metpy\calc\thermo.py", line 2410, in wet_bulb_temperature
    lcl_pressure, lcl_temperature = lcl(press, temp, dewp)
  File "C:\Users\Jack\anaconda3\envs\metpy2\lib\site-packages\metpy\xarray.py", line 677, in wrapper
    return func(*args, **kwargs)
  File "C:\Users\Jack\anaconda3\envs\metpy2\lib\site-packages\metpy\units.py", line 320, in wrapper
    return func(*args, **kwargs)
  File "C:\Users\Jack\anaconda3\envs\metpy2\lib\site-packages\metpy\calc\thermo.py", line 357, in lcl
    lcl_p = so.fixed_point(_lcl_iter, pressure.m, args=(pressure.m, w, temperature),
  File "C:\Users\Jack\anaconda3\envs\metpy2\lib\site-packages\scipy\optimize\minpack.py", line 937, in fixed_point
    return _fixed_point_helper(func, x0, args, xtol, maxiter, use_accel)
  File "C:\Users\Jack\anaconda3\envs\metpy2\lib\site-packages\scipy\optimize\minpack.py", line 891, in _fixed_point_helper
    raise RuntimeError(msg)
RuntimeError: Failed to converge after 50 iterations, value is nan

[jsillin]

Your first suggestion of

sound_wb = mpcalc.wet_bulb_temperature(sound_pres[2].values*units.hPa,sound_temps[2].values*units.degC,sound_dp[2])

also gives that same error

[jthielen]

Interesting! That looks an awful lot like #1187, but wouldn't think it is due to the same cause (and may just be the LCL calculation failing on nan temperatures. So, two ideas:

• Would you be able to test your example with a subset that doesn't have any nan values and see if that works?
• Open a full issue with this, including the test data (either original source, or just the arrays used as input to the function) that causes the failure so that one of the MetPy devs can reproduce the issue.

[dopplershift]

Capturing for the record that this has moved to a bug in #1705 .