RESTART_FILE - 30 September 2006


 In order to cut down on the perhaps unnecessarily large amounts of disk 
 usage, this release of CMAQ incorporates the implementation of a restart 
 file.  The concentration file, which is traditionally used for next-day 
 initial concentrations in multi-day scenarios, can consume large amounts 
 of disk space.  The restart file contains only the last timestamp of the 
 computational array for a run, so that it is not a large file. 
 Applications can optionally reduce the number of species and layers saved 
 to the concentration file (CONC), thereby freeing up disk space for multi-
 day scenarios.  Multi-day scenarios can now use the restart file for the 
 initial concentrations to start runs for subsequent days.

 The CONC file can be a subset of the computational grid by specifying a
 list of chemical species and/or contiguous layers in the run script
 environment variables, as is done for the average concentration (ACONC)
 file.

 If subsequent nested runs are planned from an application, they will
 require a full CONC file set (for the nested initial and boundary
 concentrations) determined by the compiled include files: GC_CONC.EXT,
 AE_CONC.EXT and NR_SPC.EXT, TR_SPC.EXT.  Since the model was compiled with
 these, the output CONC file will include their definitions if the run
 script environment variables for the "standard conc" are not declared.
 Thus, for nested runs there would be no disk usage decrease benefit for
 the coarse domain.

 Finally, if an application uses a subsetted CONC file and the model run
 should abort before the scenario end, there's no capability to restart
 where the run died, and you have to start the run again from the
 beginning.  In general, this should not prove to be a serious issue.