                     ROPP_IO Package Release v10.0
                    -------------------------------

The ropp_io module is a package of software and supporting files for
manipulating Radio Occulation (RO) data to/from the ROPP format files.

ropp_io forms one module of the Radio Occultation Processing Package (ROPP)
which is a key deliverable of the ROM SAF. The IO (input/output) of all its
sample programs is based on this 'ROPP' data format. The format itself is based
on the platform-independent netCDF data transport file mechanism.

The ROPP format is essentially mission independant, so can store RO data
processed to Level 1 and/or Level 2 from GPS/Met, CHAMP, GRACE, COSMIC or
whatever as well as from GRAS. The format was designed as an interface between
mission-dependent files and mission-independent application tools (e.g. BUFR
encoding), but could equally well be used for data exchange NRT and offline) and
for archiving.

The software provides a high-level, user-callable interface for reading and
writing RO data from/to netCDF files. The netCDF file type can contain multiple
RO profiles (a 'multifile'). Supporting routines are included to define various
composite RO data types, provide units conversions and some string handling. The
ropp_io module requires that the ropp_utils module has been installed and its
library has been built.

An example application program 'ropp2ropp' is provided which will read any
supported ROPP file, generate a file name from the contents and write the data
to back to the latest ROPP specification. This tool can also combine several
single profiles into one multifile (in one session, or a later append), split a
multifile to single profiles or thin profile data.

There are also tools to encode the data in an ROPP file to BUFR ('ropp2bufr' and
'eum2bufr') and to decode a BUFR file back to ROPP standard ('bufr2ropp') and to
convert GFZ text or UCAR netCDF files to ROPP netCDF ('gfz2ropp' and
'ucar2ropp', respectively). The BUFR tools will be built if any of the Met
Office MetDB, ECMWF BUFRDC or ECMWF ecCodes libraries is available. (In the
latter case the tools will, for now, be called 'ropp2bufr_eccodes',
'eum2bufr_eccodes', and 'bufr2ropp_eccodes'. Users who rely on a tool called,
for example, 'ropp2bufr', will therefore need to link 'ropp2bufr_eccodes' to
'ropp2bufr' in order to use the eccodes version of the tool.)

Note that, for all three BUFR libraries, an environment variable specifying the
location of the BUFR run-time tables must be set. For instance, if using the Met
Office MetDB library (v2x.y.z):

  > export BUFR_LIBRARY=$ROPP_ROOT/data/bufr

or for the ECMWF BUFRDC or ECMWF ecCodes libraries (note required trailing slash):

  > export BUFR_TABLES=$ROPP_ROOT/data/bufr/

Tools are provided to extract background profiles in ascii format from gridded
fields in GRIB file format ('grib2bgrasc') and to convert that ascii datafile
to ROPP standard ('bgrasc2ropp').

There are also tools to read 'EUMETSAT'-style RO data in netCDF-4 format, and
output in ROPP standard ('eum2ropp') or BUFR standard ('eum2bufr').

Profile thinning is implemented as a user-callable subroutine and is used by the
ropp2ropp(1) and ropp2bufr(1) tools. Various thinning algoithms are supported,
and for those that use a fixed set of output levels, these levels are
user-definable via a simple plain-text control file. Several sample control
files are included in the ropp_io/ropp directory. These may be manually copied
to a suitable location and the file and path referenced at run-time on the
command line.

See the ROPP Release Notes html file provided with the main ROPP download
tarfile for an overview and instructions for installing this module with the
build and configure tools provided with ROPP.

See the README.unix and README.cygwin files for more detailed installation
instructions and tips for experienced developers. See file MANIFEST for the
complete list of files in the distribution package and the COPYRIGHT file for
copyright information. The file INSTALL contains generic instructions for the
configure script.

Any comments on this software should be given via the ROM SAF Helpdesk at
http://www.romsaf.org


ROPP Development Team
Met Office

Version 10.0
30 September 2020
