NAME

ncdf2vdf - Transform netCDF data into a VDC

SYNOPSIS

ncdf2vdf [options] ncdf_ncdf_files... vdffile

DESCRIPTION

ncdf2vdf reads 3D and 2D variables from one or more netCDF files, wavelet transforms the data, and stores it in the VDC associated with the .vdf file vdffile. The file vdffile must first be created with the command ncdfvdfcreate

OPTIONS

-vars <vars>: Variables to convert. A colon delimited list of the 3D and 2D variables you wish to transform. Their names must appear in the .vdf file, vdffile. The default is to convert all time-varying 3D and 2D variables defined in both the .vdf file and the NetCDF files.
-numts <number>: Specify the maximum number of time steps to convert. After converting number time steps, no further processing will take place.
-stagdims <dimnames>: A colon-delimited list specifying the names of any staggered dimensions. A "staggered" dimension has dimension one greater than an unstaggered dimension. Variables defined on staggered grids are interpolated to unstaggered grids.
-startts <ts>: Integer offset of first time step in NetCDF files to be converted
-timedims <dimnames>: Colon delimited list of time dimension variable names. Any dimension names listed with this option are considered time dimensions. Data variables whose slowest varying dimension is named by this option are considered time varying.
-timevars <varnames>: Colon delimited list of time coordinate variables. If this 1D variable is present, it specfies the time in user-defined units for each time step.
-level <level>: See raw2vdf (VDC1 only)
-lod <n>: See raw2vdf (VDC2 only).
-nthreads <n>: See raw2vdf (VDC2 only).
-help: Print a usage statement and then exit.
-quiet: Operate quietly, only reporting fatal errors.

EXAMPLES

Implicit time steps

Assuming the variables in your NetCDF files do not have an explicit time dimension the command:

    ncdfvdfcreate -vars u:v:temp file1.nc file2.nc file3.nc mydata.vdf

will construct a VDF file, mydata.vdf that will contain the u, v, and temp variable names for all time steps found in the NetCDF files file1.nc, file2.nc, and file3.nc. Because no time dimension is specified the variables are assumed to be implicitly time varying (the time step is inferred from the postion of the file containing the variable on the command line).

Once mydata.vdf exists the variables in the NetCDF files can be transformed with the single command:

    ncdf2vdf -vars u:v:temp file1.nc file2.nc file3.nc mydata.vdf

Alternatively, each of the three NetCDF files may be processed separately:

    ncdf2vdf -vars u:v:temp -starts 0 file1.nc mydata.vdf

    ncdf2vdf -vars u:v:temp -starts 1 file2.nc mydata.vdf

    ncdf2vdf -vars u:v:temp -starts 2 file3.nc mydata.vdf

Explicit time steps

Assuming that your NetCDF files have an explicit time dimension with NetCDF dimension name times, the command

    ncdfvdfcreate -timedims times -vars u:v:temp file1.nc file2.nc file3.nc mydata.vdf

will generate an appropriate .vdf file. This example is identical to the previous example, except that here the variables are expected to be explicitly time varying, having their slowest varying dimension named "times". Once the mydata.vdf file has been created the variables may be transformed with ncdf2vdf using the command:

    ncdf2vdf -timedims times -vars u:v:temp file1.nc file2.nc file3.nc mydata.vdf

to convert all variables at once. If the time dimesion is of length 10 individual files may be processed by the sequence of commands:

    ncdf2vdf -timedims times -vars u:v:temp -starts 0 file1.nc mydata.vdf

    ncdf2vdf -timedims times -vars u:v:temp -starts 10 file2.nc mydata.vdf

    ncdf2vdf -timedims times -vars u:v:temp -starts 20 file3.nc mydata.vdf

Time coordinate variable

If in addition to a time dimension, named "times", your NetCDF files contain a time coordinate variable, also named "times" (a one-dimensional variable dimentioned by "times", and containing monotonically increasing values), the following command should be used to generate the .vdf file:

    ncdfvdfcreate -timedims times -timevar times file1.nc file2.nc file3.nc mydata.vdf

Note that the names of the variables were not specified to the ncdfvdfcreate command as in the previous examples. In this case all 2D and 3D time-varying variables present in the NetCDF files will be identified.

All appropriate, detected variables may then be transformed with the command:

    ncdf2vdf -timedims times -timevar times file1.nc file2.nc file3.nc mydata.vdf

HISTORY

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