Hi Becky- Never mind the bundle, I figured it out. > We got a report from a McIDAS-V user that their loop of grib2 data > showed missing data, even though the file has no missing data. Here's a > link to the loop he sent - > http://cimss.ssec.wisc.edu/model/realtime/cras45_NA/grib2/ > > We were able to duplicate this in both McIDAS-V and the nightly build of > IDV. Any idea what's going on? the problem is that there are missing points in the u component of the wind field, so when absolute vorticity is calculated at those points, the values end up as missing since there is no u component. I'm not sure how McIDAS fills in the gaps at the grid points, but it seems to me that if you don't have wind values at a point, you can't calculate the vorticity. I am surprised that there are vectors plotted at some of the points with a missing v, though. Although that might be due to a weighted average sampling somewhere along the way. Attached is a plot of the wind vectors over the absolute vorticity field overlain with the vector vield and value plots of the u (top) and v (bottom) components. Notice that the holes line up with the areas where there are missing u values. So, the question is why are there gaps in the u wind field. Is it in the data or a problem in the grib decoding layer? I'll look a little closer at the data tomorrow, but if you have investigate on your end also, that would help. It would be interesting to know what McIDAS does with missing data. > Here are screen shots of McV, McX, and -X output of grid statistics from > the GRDINFO command. If you'd like to grab it, I put the grib2 file in > ftp://ftp.ssec.wisc.edu/pub/incoming/20080712.00z.cras45_NA.grib2 Does McIDAS ignore missing values when it plots the statistics? > I think that's everything, but let me know if you need any more > information from me. Don Ticket Details =================== Ticket ID: UNX-198008 Department: Support IDV Priority: Normal Status: Open
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