问Metpy中平流计算中的问题

EN

/usr/local/lib/python3.8/dist-packages/metpy/xarray.py:1445: UserWarning: Vertical dimension number not found. Defaulting to (..., Z, Y, X) order.
  warnings.warn(
Traceback (most recent call last):
  File "temp_avect_calc.py", line 33, in <module>
    adv = mpcalc.advection(q, [u, v], (dx, dy))
  File "/usr/local/lib/python3.8/dist-packages/metpy/xarray.py", line 1470, in wrapper
    grid_deltas_from_dataarray(grid_prototype, kind='actual')
  File "/usr/local/lib/python3.8/dist-packages/metpy/xarray.py", line 1380, in grid_deltas_from_dataarray
    geod=f.metpy.pyproj_crs.get_geod()))
  File "/usr/local/lib/python3.8/dist-packages/metpy/xarray.py", line 253, in pyproj_crs
    return self.crs.to_pyproj()
  File "/usr/local/lib/python3.8/dist-packages/metpy/xarray.py", line 233, in crs
    raise AttributeError('crs attribute is not available.')
AttributeError: crs attribute is not available.

import cartopy.crs as ccrs
import metpy.calc as mpcalc
from metpy.units import units
import xarray as xr

fname  =  "uwnd_vwnd_shum_750hPa_2019.nc"
ds = xr.open_dataset(fname)

lat = ds["latitude"][::-1]
lon = ds["longitude"]


u = ds["u"][:,  ::-1, :] 
v = ds["v"][:,  ::-1, :] 
q = ds["q"][:,  ::-1, :] 


dx, dy = mpcalc.lat_lon_grid_deltas(lon, lat)

adv = mpcalc.advection(q, [u, v], (dx, dy))