Make CAMx inputs from new NWP

PseudoNetCDF can read many formats (NetCDF=yes, grib1=not yet) and write out many formats (all CAMx binary inputs=yes).

I would start by trying to create input data from your NWP for a known case, like the CAMx testcase. The code below should get you started. It was written as a quick response and may contain typos.

import shutil
from PseudoNetCDF import PNC
input_nc_path = '/path/to/some/file.nc'
template_uamiv_path = '/path/to/camx/testcase/camxv6.2d_met.20020603.12k.bin'
output_uamiv_path = '/path/to/camx/newcase/input.uamiv'

# copy an existing file
shutil.copy(template_uamiv_path, output_uamiv_path)

# pncargs includes all specified and inferred options as well as
# ifiles - a list of read files
inpncargs = PNC(input_nc_path)
infile = inpncargs.ifiles[0]
outpncargs = PNC('--format=uamiv,mode=“r+“', output_uamiv_path)
outfile = outpncargs.ifiles[0]

# this is where we update the input variables
for varkey, varobj in outfile.variables.items():
    # ... create a variable of new values newvalues ...
    #     ... get a variable from infile ...
    #     ... do some processing and data translation ...
    # ... newvalues must be consistent in shape and units (see CAMx mannual) ...
    # ... as a silly example, I set the new values to the old values ...
    newvalues = varobj[:]

    # Assign new values to variable
    varobj[:] = newvalues
    # Syncing is not strictly necessary, but always make me feel safer
    outfile.sync()

# For a known case that is intended to be the same, this might not be necessary
for propkey in outfile.ncattrs():
    oldpropval = getattr(outfile, propkey)
    # ... create a variable with the new value
    # ... as a silly example, I set the new value to the old value ...
    newpropval = oldpropval
    setattr(outfile, propkey, newpropval)
    print(propk, 'old:', oldpropval, 'new:', newpropval)

You can also create CAMx inputs without copying an existing one. That relies more on creating a PseudoNetCDF file and variables that look like a CAMx file. To see one, run the following command:

pncdump --header --format=uamiv /path/to/camx/testcase/camxv6.2d_met.20020603.12k.bin

You can create one with commands like:

from PseudoNetCDF import PseudoNetCDFFile
from PseudoNetCDF.pncgen import pncgen

newf = PseudoNetCDFFile()
newf.createDimension('TSTEP', 25)
newf.createDimension('LAY', ?)
newf.createDimension('ROW', ?)
newf.createDimension('COL', ?)
newf.createDimension('DATE-TIME', 2)
newf.createDimension('VAR', ?)
newf.NROWS = ?
newf.NCOLS = ?
...
newf.XORIG = ?
...
newf.createDimension('COL', ?)

var = newf.createVariable(...)
var.units = '...'
var[:] = '...'

pncgen(newf, '/path/for/output.bin', format = 'uamiv')

barronh / pseudonetcdf

Make CAMx inputs from new NWP #22