NCAR CSM Flux Coupler, version 4.0 -- User's Guide         Table of Contents

3   Output Data

The Flux Coupler outputs three types of data:

 §3.1  stdout output   (ASCII text)
 §3.2  restart files   (machine specific binary)
 §3.3  history files   (netCDF format, instantaneous and/or mean monthly data)

3.1   Stdout Output

Stdout (standard out) output consists mostly of brief messages that indicate how the simulation is progressing and whether any error conditions have been detected. Stdout also contains a record of the values of all Coupler input parameters. If global diagnostics have been activated, by setting the appropriate Coupler input parameter, stdout will also contain some diagnostic information

The Coupler's stdout, combined with stderr, is saved by the top level NQS batch job script to a directory specified by the the environment variable $LOGDIR, see  § 4. The Coupler's restart and history files are stored on NCAR's Mass Storage System (MSS). Restart files are in a machine dependent binary representation, whereas history files are in netCDF format. While most of the coupled run output data to be analyzed is assumed to be created by the various component models, the Coupler also creates output history files.

3.2   Restart Files

Restart files are in a machine dependent binary representation. Because all fields from the restart file can be saved onto a history file, normally there is no need to examine the contents of a restart file. If users want to examine a restart file, they will have to look at the Coupler source code to see how the file was written, and write their own program to read the file and examine its contents.

Restart files provide the Coupler with all the IC data necessary to continue (restart) a previous simulation. The Coupler does not need a restart file for an initial run, but for all other run types a restart file is required.

3.3   History Files

History File Format

NetCDF was chosen as the history data format because many common visualization tools already accept this format as input, thus facilitating the acquisition of a visualization or analysis utility to view Coupler history files. NetCDF (network Common Data Form) is an interface for array-oriented data access and a library that provides an implementation of the interface. The netCDF library also defines a machine independent format for representing scientific data. Together the interface, library, and format support the creation, access, and sharing of scientific data. The netCDF software was developed at the Unidata Program Center in Boulder, Colorado. The freely available source can be obtained by anonymous FTP from or from other mirror sites.

History File Content

Because netCDF files are self-describing, the most complete and accurate description of the contents of a Coupler history file (or any netCDF file) will always come from the netCDF data file itself. The netCDF tool "ncdump" will generate the CDL text representation of a netCDF file on standard output, optionally excluding some or all of the variable data in the output.

Three types of data are found in Coupler netCDF history data files: global attributes, domain data, and two dimensional state and flux data.

(1) Global attributes

This includes the case name corresponding to the history data and the date the data was created.

(2) Model domain data

This includes the coordinates of the grid cells of all model domains, as well as a domain mask for each surface model. Each model has two sets of strictly increasing latitude and longitude coordinates, one corresponding to grid cell centers, xc(i) and yc(j), and one corresponding to grid cell edges, xe(i) and ye(j). Note that the grid cell "centers" are typically, but not necessarily, at or near the center of a cell. A state variable S(i,j) is understood to be a point value located at (xc(i),yc(j)), which is located within a grid cell bounded by longitude coordinates xe(i) and xe(i+1) and latitude coordinates ye(j) and ye(j+1). A flux field F(i,j) can be thought of as a point value located at (xc(i),yc(j)), but more accurately it is an area average value that applies uniformly over the grid cell containing that point.

Four sets of coordinate arrays are found in the history data:

Each surface model (land, sea-ice, ocean) also has a corresponding domain mask. The domain mask is an integer array such that if mask(i,j) .ne. 0, then the indices (i,j) correspond to a grid cell that is in the active model domain, i.e., S(i,j) is a valid model state and F(i,j) is a valid flux value. Conversely, if mask(i,j) = 0, then S(i,j) and F(i,j) are undefined.

Three masks are found in the history data:

There is no atmosphere domain mask because all atmosphere data points are assumed to be valid points within the atmosphere domain.

(3) Two dimensional state and flux data

This includes model state variables, component flux fields, and merged input flux fields. The naming convention for two dimensional variables follows the convention introduced in  § 7   of this document. Some examples of state variable names are:

Some examples of flux field variable names are: Each variable in the netCDF history file has long_name and units attributes which further describe the variable. Also see  § 2   for a more complete description of such variables.

Fri 07 Aug 1998, 12:00:00