[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[python #AQS-174406]: python/netcdf data array questions


I did reproduce your advection code error, and I was able to execute the code 
and produce maps from your provided NARR_20080105_1800.nc. In this provided 
netCDF file there are dimensions of time provided for Jan 05 2018 at both 18Z 
and 21Z. The 21Z entry is is only full of NaN-data, but it still exists in the 
file. I am adapting the Differential Temperature Advection notebook available 
 and will provide my full adaptation below and attach an image of the produced 

  (imports are unedited)

  ds = xr.open_dataset('NARR_20080105_1800.nc')

  # With our dataset open, select only the first entry in the time dimension
  ds = ds.isel(time=0)

  # Get lat/lon data from file - edit for variable name
  lats = ds.latitude.data
  lons = ds.longitude.data

  # Calculate variable dx, dy values for use in calculations - no edit
  dx, dy = mpcalc.lat_lon_grid_deltas(lons, lats)

  # Get 700-hPa data and smooth - edit to make selectable
  level = 700
  hght_700 = mpcalc.smooth_n_point(ds['HGT'].sel(plevel=level).squeeze(), 9)
  tmpk_700 = mpcalc.smooth_n_point(ds['TMP'].sel(plevel=level).squeeze(), 9)
  uwnd_700 = mpcalc.smooth_n_point(ds['UGRD'].sel(plevel=level).squeeze(), 9)
  vwnd_700 = mpcalc.smooth_n_point(ds['VGRD'].sel(plevel=level).squeeze(), 9)

  # Get 300-hPa data and smooth - edit to make selectable
  level = 300
  hght_300 = mpcalc.smooth_n_point(ds['HGT'].sel(plevel=level).squeeze(), 9)
  tmpk_300 = mpcalc.smooth_n_point(ds['TMP'].sel(plevel=level).squeeze(), 9)
  uwnd_300 = mpcalc.smooth_n_point(ds['UGRD'].sel(plevel=level).squeeze(), 9)
  vwnd_300 = mpcalc.smooth_n_point(ds['VGRD'].sel(plevel=level).squeeze(), 9)

  # Convert Temperatures to degC - no edit
  tmpc_700 = tmpk_700.to('degC')
  tmpc_300 = tmpk_300.to('degC')

  # Get time in a nice datetime object format - edit to remove datetime object 
  vtime = ds.time.values

  # Use MetPy advection function to calculate temperature advection at two 
levels - no edit
  tadv_700 = mpcalc.advection(tmpk_700, (uwnd_700, vwnd_700), (dx, dy), 
  tadv_300 = mpcalc.advection(tmpk_300, (uwnd_300, vwnd_300), (dx, dy), 

  # Centered finite difference to calculate differential temperature advection 
- no edit
  diff_tadv = ((tadv_700 - tadv_300)/(400 * units.hPa)).to_base_units()

  # Set up plot crs (mapcrs) and the data crs, will need to transform all 
variables - no edit
  ... (the plotting code continues unedited)

I hope this helps, and if this doesn't work for you please follow up and let me 
know! There's no rush here, and I'll be available whenever you get time to 
dedicate to it. Thanks.

All the best,

Drew Camron

> A few quick questions/comments here:
> - Did you reproduce my error?
> - Did the code run after you added suggested edit?
> - Where did you add that edit?
> - I added this and still get same error as before, but probably I need to
> edit correctly:
> *# select one 2D field, advice from Unidatads.isel(time=0)*
> - (BTW - "dataset" is not defined so dataset.isel means nothing)
> - We just have one time step in the file, so I don't really understand your
> instruction
> I should be able to focus some on this, this afternoon.

Ticket Details
Ticket ID: AQS-174406
Department: Support Python
Priority: Low
Status: Closed
NOTE: All email exchanges with Unidata User Support are recorded in the Unidata 
inquiry tracking system and then made publicly available through the web.  If 
you do not want to have your interactions made available in this way, you must 
let us know in each email you send to us.

Attachment: index.png
Description: PNG image