MetPy Question

Greetings!

When I uncomment those lines and run with the current version of xarray (2024.7.0), I get the following error:

> 

TypeError: Variable 'Temperature_5pt_3pass': Using a DataArray object to construct a variable is ambiguous, please extract the data using the .data property.

That more helpful error leads me to add a `.data` property to the line storing the data in `narr`:

    narr['Temperature_5pt_3pass'] = (['y', 'x'], smoothed.data)

After making this change, everything runs fine for me. Does this solve it for you?

Cheers,

Ryan

Good morning, I am working through one of the MetPy Monday videos and am stuck. I was hoping that you might be able to point me in the right direction. The video I was working through is at https://www.youtube.com/watch?v=r9oMB0ZhWSk.

 

My code is below. I’ve commented out what doesn’t seem to work and I’m fairly certain I typed things as they were in the video.

 

from metpy.cbook import get_test_data

 

import xarray as xr

 

narr = xr.open_dataset(get_test_data('narr_example.nc', as_file_obj=False))

 

from metpy.plots.declarative import *

from metpy.units import units

 

import metpy.calc as mpcalc

smoothed = mpcalc.smooth_n_point(narr['Temperature'].sel(isobaric=850).isel(time=0), 5, 3)

#narr['Temperature_5pt_3pass'] = (['y','x'],smoothed)

#narr['Temperature_5pt_3pass'].attrs = narr['Temperature'].attrs

 

contour_raw = ContourPlot()

contour_raw.data = narr

contour_raw.field = 'Temperature'

contour_raw.level = 850 * units.hPa

contour_raw.linecolor= 'tab:red'

contour_raw.linewidth = 1

contour_raw.linestyle = '--'

contour_raw.contours = 15

 

#contour_smooth = ContourPlot()

#contour_smooth.data=narr

#contour_smooth.field = 'Temperature_5pt_3pass'

#contour_smooth.linecolor = 'tab:blue'

#contour_smooth.linewidth = 1

#contour_smooth.linestyle = '--'

#contour_smooth.contours = 15

 

panel = MapPanel()

panel.area = 'co'

panel.layers = ['coastline','borders', 'states']

panel.title = 'Smoothing of 850hPa Temperatures'

panel.plots = [contour_raw]

 

pc = PanelContainer()

pc.size = (10,8)

pc.panels = [panel]

pc.show()

 

 

The error I get is

 

PS C:\Users\User\Dropbox\Python>  & 'c:\Users\User\AppData\Local\Programs\Python\Python312\python.exe' 'c:\Users\User\.vscode\extensions\ms-python.debugpy-2024.10.0-win32-x64\bundled\libs\debugpy\adapter/../..\debugpy\launcher' '60022' '--' 'c:\Users\User\Desktop\Test\test.py'

PS C:\Users\User\Dropbox\Python> ^C

PS C:\Users\User\Dropbox\Python>

PS C:\Users\User\Dropbox\Python>  c:; cd 'c:\Users\User\Dropbox\Python'; & 'c:\Users\User\AppData\Local\Programs\Python\Python312\python.exe' 'c:\Users\User\.vscode\extensions\ms-python.debugpy-2024.10.0-win32-x64\bundled\libs\debugpy\adapter/../..\debugpy\launcher' '60062' '--' 'c:\Users\User\Desktop\Test\test.py'

PS C:\Users\User\Dropbox\Python> ^C

PS C:\Users\User\Dropbox\Python>

PS C:\Users\User\Dropbox\Python>  c:; cd 'c:\Users\User\Dropbox\Python'; & 'c:\Users\User\AppData\Local\Programs\Python\Python312\python.exe' 'c:\Users\User\.vscode\extensions\ms-python.debugpy-2024.10.0-win32-x64\bundled\libs\debugpy\adapter/../..\debugpy\launcher' '60086' '--' 'c:\Users\User\Desktop\Test\test.py'

Traceback (most recent call last):

  File "c:\Users\User\AppData\Local\Programs\Python\Python312\Lib\site-packages\xarray\core\dataset.py", line 1477, in _construct_dataarray

    variable = self._variables[name]

               ~~~~~~~~~~~~~~~^^^^^^

KeyError: 'Temperature_5pt_3pass'

 

During handling of the above exception, another exception occurred:

 

Traceback (most recent call last):

  File "c:\Users\User\AppData\Local\Programs\Python\Python312\Lib\site-packages\xarray\core\dataset.py", line 1576, in __getitem__

    return self._construct_dataarray(key)

           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

  File "c:\Users\User\AppData\Local\Programs\Python\Python312\Lib\site-packages\xarray\core\dataset.py", line 1479, in _construct_dataarray

    _, name, variable = _get_virtual_variable(self._variables, name, self.sizes)

                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

  File "c:\Users\User\AppData\Local\Programs\Python\Python312\Lib\site-packages\xarray\core\dataset.py", line 213, in _get_virtual_variable

    raise KeyError(key)

KeyError: 'Temperature_5pt_3pass'

 

The above exception was the direct cause of the following exception:

 

Traceback (most recent call last):

  File "c:\Users\User\Desktop\Test\test.py", line 43, in <module>

    pc.show()

  File "c:\Users\User\AppData\Local\Programs\Python\Python312\Lib\site-packages\metpy\plots\declarative.py", line 200, in show

    self.draw()

  File "c:\Users\User\AppData\Local\Programs\Python\Python312\Lib\site-packages\metpy\plots\declarative.py", line 187, in draw

    panel.draw()

  File "c:\Users\User\AppData\Local\Programs\Python\Python312\Lib\site-packages\metpy\plots\declarative.py", line 511, in draw

    p.draw()

  File "c:\Users\User\AppData\Local\Programs\Python\Python312\Lib\site-packages\metpy\plots\declarative.py", line 891, in draw

    self._build()

  File "c:\Users\User\AppData\Local\Programs\Python\Python312\Lib\site-packages\metpy\plots\declarative.py", line 1062, in _build

    x_like, y_like, imdata = self.plotdata

                             ^^^^^^^^^^^^^

  File "c:\Users\User\AppData\Local\Programs\Python\Python312\Lib\site-packages\metpy\plots\declarative.py", line 875, in plotdata

    plot_x_dim = self.griddata.metpy.find_axis_number('x')

                 ^^^^^^^^^^^^^

  File "c:\Users\User\AppData\Local\Programs\Python\Python312\Lib\site-packages\metpy\plots\declarative.py", line 819, in griddata

    data = self.data.metpy.parse_cf(self.field)

           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

  File "c:\Users\User\AppData\Local\Programs\Python\Python312\Lib\site-packages\metpy\xarray.py", line 817, in parse_cf

    var = self._dataset[varname]

          ~~~~~~~~~~~~~^^^^^^^^^

  File "c:\Users\User\AppData\Local\Programs\Python\Python312\Lib\site-packages\xarray\core\dataset.py", line 1578, in __getitem__

    raise KeyError(

KeyError: "No variable named 'Temperature_5pt_3pass'. Variables on the dataset include ['Temperature', 'time', 'isobaric', 'y', 'x', ..., 'lon', 'u_wind', 'v_wind', 'Geopotential_height', 'Specific_humidity']"

PS C:\Users\User\Dropbox\Python>