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Previous: GEMPAK Grid Data Types Next: GEMPAK Grid Program Exercises!! (Scalar Values) Table of contents Frames User Manual GEMPAK Online Tutorial > GEMPAK Grid Programs

7.1 GEMPAK Grid Plotting Programs

Some new Variables

Plotting gridded data requires some additional variables for specifying the grid to be used.

  • GDFILE
  • GDATTIM
  • GLEVEL
  • GVCORD
  • GFUNC
  • GVECT
  • GDPFUN(gdplot2 only)

    Most of these variables are directly to analogous to their counterparts used for plotting surface and upper air data. One addition is the notion of a valid time in the GDATTIM variable. Since model output has both an initial or verification time and a valid time, we need an additional field appended to the nominal model time to represent when the forecast is valid.

    GFUNC represents a scalar quantity to be plotted, while GVECT represents a vector quantity. GDPFUN encompasses both scalar and vector quantities. The GFUNC/GVECT/GDPFUN variable can either be a variable name which resides within the grid file, a grid which can be derived from other fields found in the grid file, or one of the mathematical or meteorological operators listed in GPARM. When using the operators listed in GPARM, remember that fields marked S require a scalar variable, and fields marked V require a vector.

    Now a few more variables to think about:

  • CTYPE determines whether a line or filled area is drawn in countour plots.
  • TYPE used in GDPLOT2 is a superset of CTYPE, and includes additional selections for streamlines, markers and point data.
  • CINT is the line contour interval.
  • FINT is the filled area contour interval.
  • LINE attributes for line contours.
  • FLINE attributes for filled area contours.

    Well, as you will see there are many more variables, but these will get you going.

    Trial by fire is probably the best way to deal with these programs! Lets do some exercises!

     


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