GEMPAK, the GEneral Meteorology PAcKage, is a suite of applications programs for the analysis, display and diagnosis of geo-referenced data. GEMPAK was orginially developed by the Severe Storms Laboratory at the Goddard Space Flight Center of NASA starting in the early 1980's. The Unidata program center release of GEMPAK/N-AWIPS incorporates several additions developed both locally and at COMET to enhance the use of realtime data aquired through the IDD, as well as instructional case studies.
As a software package, GEMPAK is made up of application programs, libraries, graphics routines, and device drivers. Each time GEMPAK is used to analyze and display data some or all of these components are used. For example, the user runs an application program like SFMAP, the surface mapping program. In order to do the scientific data analysis that GEMPAK is so well known for, the application program calls on a suite of library routines which do everything from parsing your input to calculating complicated grid diagnostics.
When the graphic is ready to be constructed, the application program (SFMAP) starts up a separate graphics program. This GPLT graphics process handles all the graphics processing including mapping, symbol drawing, and coordinate transformations. When the graphic is ready to be output, a third process called the device driver starts up. The device driver could be any one of several GEMPAK drivers available. For example, it could be a process to draw the picture to an XWindow (XW) or a GIF image or it could be a process to write out instructions to a Postscript file (PS).
This workshop will use a Linux terminal window (a shell) to run GEMPAK programs. When you launch the terminal you are in the gempak user's home directory /home/gempak/ (or ~ for short). You will need to edit the file ~/.cshrc to source the GEMPAK environmental variable file /home/gempak/NAWIPS/Gemenviron:
Edit the file with vi:
vi .cshrc
and add the line
source /home/gempak/NAWIPS/Gemenviron
save the file with the command :wq, close the terminal window and launch another one. In this new window, check that the GEMPAK variables are sourced with the command env | grep GEM; it should look like this:
gempak@workshop:~> env | grep GEM
NAWIPS=/home/gempak/GEMPAK6.6.0
GEM_COMPTYPE=gfortran
GEMPAK=/home/gempak/GEMPAK6.6.0/gempak
GEMPAKHOME=/home/gempak/GEMPAK6.6.0/gempak
CONFIGDIR=/home/gempak/GEMPAK6.6.0/config
OS_ROOT=/home/gempak/GEMPAK6.6.0/os/linux64
OS_BIN=/home/gempak/GEMPAK6.6.0/os/linux64/bin
OS_INC=/home/gempak/GEMPAK6.6.0/os/linux64/include
OS_LIB=/home/gempak/GEMPAK6.6.0/os/linux64/lib
GEMLIB=/home/gempak/GEMPAK6.6.0/os/linux64/lib
GEMEXE=/home/gempak/GEMPAK6.6.0/os/linux64/bin
GEMPDF=/home/gempak/GEMPAK6.6.0/gempak/pdf
GEMTBL=/home/gempak/GEMPAK6.6.0/gempak/tables
GEMERR=/home/gempak/GEMPAK6.6.0/gempak/error
GEMHLP=/home/gempak/GEMPAK6.6.0/gempak/help
…
GEMPAK programs are located in the directory ~/NAWIPS/os/linux/bin/, or $OS_BIN for short.