Data files in the CMAQ system can be easily manipulated by using the netCDF and I/O API utilities. Information regarding the most commonly employed utility routines is listed in Table 4.5, and they are further described in the following sections.
Table 4.5. CMAQ data manipulation utilities
| Utility | Description |
|---|---|
| NCDUMP | print file as structured ASCII; from NCAR |
| M3XTRACT | extract a subset of variables from a file for a specified time interval |
| M3DIFF | compute statistics for pairs of variables |
| M3STAT | compute statistics for variables in a file |
| BCWNDW | build a boundary-condition file for a sub-grid window of a gridded file |
| M3EDHDR | edit header attributes/file descriptive parameters |
| M3TPROC | compute time period aggregates and write them to an output file |
| M3TSHIFT | copy/time shift data from a file |
| M3WNDW | window data from a gridded file to a sub-grid |
| M3FAKE | build a file according to user specifications, filled with dummy data |
| VERTOT | compute vertical-column totals of variables in a file |
| UTMTOOL | coordinate conversions and grid-related computations for Lat/Lon, Lambert, and UTM |
This program generates an ASCII representation of a netCDF file, either with or without an ASCII representation of the variable data in the file. NCDUMP was produced by the University Corporation for Atmospheric Research (the originators of netCDF) and is distributed by Unidata. This utility program is useful in determining the dimensions and contents of a MAQSIP file. The syntax for invoking ncdump in UNIX is the following
ncdump [-h] [-c] [-n name] [inputfile]
where:
-h produces only the "header" information in the output file (i.e., the declarations of dimensions, variables, and attributes, but no data values for the variables)
-c produce the "header" information in the output file and the data values for coordinate variables
-n name