Hi Brian, I've been playing around with this and while I'm not certain I have a useful solution or workaround, I can say that DCGRIB2 is decoding the LAPS grib2 files correctly. Rather than plot the function PVOR(THTA,WND) I've plotted the layer difference LDF(THTA) for 300:200. In the first image attached (GEMPAK_thta.gif), contoured on top of this layer difference is THTA @ 300 (black) and THTA @ 200 (white). It's clear to see that the discontinuities in the layer difference field appear because of the value of THTA at these two levels. Compare to an image of 300:200mb difference for THTA produced by the IDV (IDV_thta.gif) using the LAPS grib2 file and you see the same artifacts (you'll have to ignore/excuse the white block artifacts - I'm not sure why these appear). So it appears DCGRIB2 is doing it's job correctly, but that answer doesn't help you much since the layer difference for THTA doesn't look natural plotted in either GEMPAK or IDV. What I can suggest is you play around with different values for IJSKIP, FINT and CONTUR which should help you lessen the visual impact of these "noodles". What software package are you using which produced PVOR plots (and I should ask THTA difference plots) without these artifacts? Michael James Unidata > Hello! > > I'm using GDCNTR with these parameters: > > GDATTIM = last > GLEVEL = 300:200 > GVCORD = pres > GFUNC = pvor(thta,obs) > GDFILE = 081432000.gem > CINT = 2 > LINE = 3 > MAP = 1 > MSCALE = > TITLE = 1 > DEVICE = xw > SATFIL = > RADFIL = > IMCBAR = > PROJ = > GAREA = grid > IJSKIP = > CLEAR = yes > PANEL = 0 > TEXT = 1 > SCALE = 999 > LATLON = > HILO = > HLSYM = > CLRBAR = > CONTUR = 0 > SKIP = > FINT = 2 > FLINE = 30-8 > CTYPE = f > LUTFIL = > STNPLT = > > and the plot is showing what I can only describe as "noodles" of potential > vorticity. > Another plotting program used the grib data file directly and didn't produce > this > effect. Does dcgrib2 maintain the precision of the original grib file? > > The grid is a LAPS grid nest, and I put the grib file and my dcgrib2 decoded > .gem > file here in case you want to take a look: > > http://www-frd.fsl.noaa.gov/mab/jamison/tmp/ > > > Please let me know, thanks! > > Brian Jamison > > > > Ticket Details =================== Ticket ID: XFV-201111 Department: Support GEMPAK Priority: Normal Status: Open
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