Frequently Asked Questions

Q1: How do I get help if my questions are not answered in the User's Guide?
A: First, refer to the documentation on this website. If that doesn't answer your question, then email: gsi_help@ucar.edu.

Q2: How do I reference the GSI User's Guide in publications?
A: Please reference the GSI User's Guide (including the version number) as follows:
Developmental Testbed Center, 2011:
Gridpoint Statistical Interpolation (GSI) User's Guide for Version 3.0
Available at http://www.dtcenter.org/com-GSI/users/docs/index.php.
145 pp.

Q3: When running GSI on Linux platforms, there is a problem reading prepbufr files obtained from the NCEP ftp server and/or the file gdas1.t12z.prepbufr.nr from the tutorial exercise, but not the file newgblav.gdas1.t12z.prepbufr.nr.
A: This is what is known as the Endian problem. Different computer hardware platforms may use different byte order to representation information. For details see the Wikipedia article on Endianness . Typically this is only an issue on current systems when sharing binary IO between an IBM ("Big-Endian") and Linux system ("Little Endian").

The prepbufr format is such a binary IO format. The prepbufr files from the NCEP ftp server, or the file gdas1.t12z.prepbufr.nr from the tutorial exercises, were generated on an IBM. In contrast, the file newgblav.gdas1.t12z.prepbufr.nr is a byte-swapped version of the prepbufr file gdas1.t12z.prepbufr.nr. This conversion was conducted using the C code ssrc.c located in the /utils directory of the GSI distribution. This byte-swapping code will take a prepbufr file generated on an IBM platofrm and convert it to a prepbufr file that can be read on a Linux or Intel Mac platform.

Compile ssrc.c with any c compiler. To convert an IBM prepbufr file, take the executable (e.g. ssrc.exe), and run it as follows:
ssrc.exe < name of Big Endian prepbufr file > name of Little Endian prepbufr file