6.2. Basic CMAQ Output Files

6.2. Basic CMAQ Output Files
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6.2.1. CMAQ Output Log
6.2.2. CONC: CCTM hourly instantaneous concentration file
6.2.3. ACONC: CCTM hourly average concentration file
6.2.4. DRYDEP: CCTM hourly cumulative dry deposition file
6.2.5. WETDEP: CCTM hourly cumulative wet deposition file
6.2.6. AEROVIS: CCTM hourly instantaneous visibility metrics

As all of the CMAQ programs produce output files that are input to other CMAQ programs, differentiating between CMAQ input and output is not entirely clear. The previous section dealt with the output files from JPROC, ICON, BCON, and MCIP as inputs to the CCTM. In this section, we will detail the general structure of all CMAQ binary outputs and provide details on the CCTM output files.

All CMAQ programs, other than JPROC, produce output files that adhere to the IO API format (Chapter 8); JPROC produces ASCII output files. The IO API formatted CMAQ output files are 3-dimensional gridded, time-stepped binary files that contain headers with metadata describing the file contents. These machine-independent and network transparent binary files are transferable between different computer architectures. The advantages of using the IO API output format include (Coats, 2005),

performance: visualization and analysis programs looking at selected parts of the data don't need to read unrequested data from the files.
modularity: data can be read or written in any order (or not at all). The same input files can serve both simple engineering models and full-chemistry models -- the former reading just a few of the variables from the files, the latter reading most of them. The modular-model structure used for CMAQ depends upon this feature.
robustness: data are "tagged" by name, date, and time; miscounted record-numbers don't scramble temperatures with pressures, for example.

The IO API output data are written to files using calls to the WRITE3 logical IO/API function. The amount of information saved to CMAQ output files is defined almost entirely by the developer of a particular subroutine. Should a user decide additional (or less) output is needed, simple code changes could be completed to add (or remove) the selected data. For example, in the current release version of CMAQ (version 4.5) the coefficients of vertical eddy diffusivity are not written to any output file. However, the physical Kv values are calculated in the model in the subroutine EDYINTB and contravariant diffusivities are computed in the VCONTDIFF subroutine. It would be a relatively simple matter to insert code to output the values, either as a new individual output file or as an appendage to an existing file.

In addition to model data output, CMAQ can optionally produce log files containing the standard output from the different CMAQ processors. If the log file option is not selected by the user, CMAQ will write all of the log information to the screen along with the standard error, which can be captured to a text file using basic Unix syntax.

6.2.1. CMAQ Output Log

All of the CMAQ processors generate standard output and standard error during execution. For all of the processors other than the CCTM, this diagnostic output information can be captured to a log file at execution using a Unix redirect command. For example to capture the standard output and error of a BCON simulation, use the following command:

run.bcon.csh >& run.bcon.log

For the CCTM the "LOGFILE" environment variable allows users to specify the name of a log file for capturing the standard output from the program. If this variable is not set, the standard output is written to the terminal and can be captured using the Unix redirect command (">"), as shown in the example above.