Hi John, I hope it works via E-Mail…? Thanks, Jochen
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Am 18.11.2013 um 17:01 schrieb John Caron <caron@xxxxxxxxxxxxxxxx>: > Hi Jochen: > > Yes, please send us the single grib record, so we can test. > > thanks! > > John > > On 11/15/2013 6:04 AM, Jochen Kähler wrote: >> Hi all, >> >> we’re implementing some service that reads ECMWF 0.125° Grib files in >> gaussian grid. The NetCDF-Library automatically interpolates the >> gaussian grid to a regular lat/lon-grid. For the relative humidity we >> found some strange values in output after that interpolation. >> >> Using wgrib I’ve extracted some isobaric relative humidity record to a >> single grib file called „dpd_test.grib“ (which i could send as well if >> needed). According to wgrib, it is an gaussian grid and min and max >> values are 0% and 100% - as I would expect them for a relative humidity >> (see attached output). >> >> Next I’ve written a small program which extracts that relative humidity >> parameter via netcdf-java-lib and step thru all values to find minimum >> and maximum in it. Source is also attached - just in case I did >> something wrong there. >> >> The output of that states the following... >> 2013-11-14 13:45:15,378 INFO : App - >> dpd_test.grib/Relative_humidity_isobaric/850.0hPa: >> min=-4.462653160095215 max=108.53846740722656 >> …indicating the minimum relative humidity is around -4.46% and the >> maximum at 108.54%. >> >> Browsing your code on Github I think you’re using cubic interpolation to >> convert gaussian to regular grid, which might cause this problem. >> https://github.com/Unidata/thredds/blob/6b1052455e597797f3a5980165a23292172920ce/grib/src/main/java/ucar/nc2/grib/QuasiRegular.java >> Line >> 219 - 221: >> outpt[oIdx] = (float) (a * inpt[iIdx + low] + b * inpt[iIdx + hi] >> + ((a * a * a - a) * y2d[low] >> + (b * b * b - b) * y2d[hi]) / 6.0); >> Is the problem in the parametrization of this formula? >> >> Is it possible to use Linear Interpolation here? >> >> Kind Regards, >> Jochen >> >> >> >> — wgrib output --------------- >> Losty-MacBook:Desktop jkaehler$ ~/wgrib/wgrib -V dpd_test.grib >> rec 1:0:date 2013111300 R kpds5=157 kpds6=100 kpds7=850 levels=(3,82) >> grid=255 850 mb 6hr fcst: >> R=Relative humidity [%] >> timerange 0 P1 6 P2 0 TimeU 1 nx -1 ny 800 GDS grid 4 num_in_ave 0 >> missing 0 >> center 98 subcenter 0 process 143 Table 128 scan: WE:NS winds(N/S) >> thinned gaussian: lat 89.828000 to -89.828000 >> long 0.000000 to 359.900000, 843490 grid pts (-1 x 800) >> scan 0 mode 0 bdsgrid 1 >> 18 25 32 40 45 50 60 60 72 72 75 81 90 >> 96 100 >> 108 120 120 125 128 144 144 150 160 160 180 180 192 >> 192 200 >> 200 216 216 225 240 240 240 250 250 256 270 288 288 >> 288 300 >> 300 320 320 320 324 360 360 360 360 360 360 375 375 >> 384 400 >> 400 400 405 432 432 432 432 450 450 450 480 480 480 >> 480 480 >> 486 500 500 512 512 540 540 540 540 540 576 576 576 >> 576 576 >> 576 600 600 600 600 640 640 640 640 640 640 640 648 >> 675 675 >> 675 675 675 720 720 720 720 720 720 720 729 729 750 >> 750 750 >> 750 768 768 768 800 800 800 800 800 800 810 864 864 >> 864 864 >> 864 864 864 864 864 864 900 900 900 900 900 900 900 >> 960 960 >> 960 960 960 960 960 960 960 960 960 960 972 972 1000 >> 1000 1000 >> 1000 1000 1000 1024 1024 1024 1024 1024 1080 1080 1080 1080 1080 >> 1080 1080 >> 1080 1080 1080 1080 1125 1125 1125 1125 1125 1125 1125 1125 1125 >> 1152 1152 >> 1152 1152 1152 1152 1200 1200 1200 1200 1200 1200 1200 1200 1200 >> 1200 1200 >> 1215 1215 1215 1215 1280 1280 1280 1280 1280 1280 1280 1280 1280 >> 1280 1280 >> 1280 1280 1280 1280 1280 1296 1296 1296 1296 1350 1350 1350 1350 >> 1350 1350 >> 1350 1350 1350 1350 1350 1350 1350 1350 1350 1440 1440 1440 1440 >> 1440 1440 >> 1440 1440 1440 1440 1440 1440 1440 1440 1440 1440 1440 1440 1440 >> 1440 1440 >> 1440 1440 1440 1440 1440 1440 1440 1458 1458 1458 1458 1458 1458 >> 1458 1500 >> 1500 1500 1500 1500 1500 1500 1500 1500 1500 1500 1500 1500 1500 >> 1500 1500 >> 1500 1536 1536 1536 1536 1536 1536 1536 1536 1536 1536 1536 1536 >> 1536 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1500 1500 1500 1500 1500 1500 1500 1500 1500 >> 1500 1500 >> 1500 1500 1500 1500 1500 1500 1458 1458 1458 1458 1458 1458 1458 >> 1440 1440 >> 1440 1440 1440 1440 1440 1440 1440 1440 1440 1440 1440 1440 1440 >> 1440 1440 >> 1440 1440 1440 1440 1440 1440 1440 1440 1440 1440 1440 1350 1350 >> 1350 1350 >> 1350 1350 1350 1350 1350 1350 1350 1350 1350 1350 1350 1296 1296 >> 1296 1296 >> 1280 1280 1280 1280 1280 1280 1280 1280 1280 1280 1280 1280 1280 >> 1280 1280 >> 1280 1215 1215 1215 1215 1200 1200 1200 1200 1200 1200 1200 1200 >> 1200 1200 >> 1200 1152 1152 1152 1152 1152 1152 1125 1125 1125 1125 1125 1125 >> 1125 1125 >> 1125 1080 1080 1080 1080 1080 1080 1080 1080 1080 1080 1080 1024 >> 1024 1024 >> 1024 1024 1000 1000 1000 1000 1000 1000 972 972 960 960 960 >> 960 960 >> 960 960 960 960 960 960 960 900 900 900 900 900 900 >> 900 864 >> 864 864 864 864 864 864 864 864 864 810 800 800 800 >> 800 800 >> 800 768 768 768 750 750 750 750 729 729 720 720 720 >> 720 720 >> 720 720 675 675 675 675 675 648 640 640 640 640 640 >> 640 640 >> 600 600 600 600 576 576 576 576 576 576 540 540 540 >> 540 540 >> 512 512 500 500 486 480 480 480 480 480 450 450 450 >> 432 432 >> 432 432 405 400 400 400 384 375 375 360 360 360 360 >> 360 360 >> 324 320 320 320 300 300 288 288 288 270 256 250 250 >> 240 240 >> 240 225 216 216 200 200 192 192 180 180 160 160 150 >> 144 144 >> 128 125 120 120 108 100 96 90 81 75 72 72 60 >> 60 50 >> 45 40 32 25 18 >> min/max data 0 100 num bits 8 BDS_Ref 0 DecScale 0 BinScale -1 >> —— >> >> >> — Java-Source —— >> GridDataset dataset = GridDataset.open(gribFile.getAbsolutePath()); >> >> try { >> GridDatatype grid = dataset.findGridDatatype("Relative_humidity_isobaric"); >> if(grid != null) { >> CoordinateAxis1D isbl = grid.getCoordinateSystem().getVerticalAxis(); >> double[] isblValues = isbl.getCoordValues(); >> for (int isblIdx = 0; isblIdx < isblValues.length; isblIdx++) { >> double[] data = (double[]) grid.readDataSlice(0, isblIdx, -1, >> -1).get1DJavaArray(double.class); >> double min = Double.MAX_VALUE; >> double max = Double.MIN_VALUE; >> for (double d : data) { >> min = Math.min(min, d); >> max = Math.max(max, d); >> } >> LOG.info("{}/{}/{}{}: min={} max={}", gribFile.getName(), >> grid.getFullName(), isblValues[isblIdx], isbl.getUnitsString(), min, max); >> } >> } >> } finally { >> if (dataset != null) { >> dataset.close(); >> } >> } >> >> -------- >> >> >> _______________________________________________ >> netcdf-java mailing list >> netcdf-java@xxxxxxxxxxxxxxxx >> For list information or to unsubscribe, visit: >> http://www.unidata.ucar.edu/mailing_lists/ >> > > _______________________________________________ > netcdf-java mailing list > netcdf-java@xxxxxxxxxxxxxxxx > For list information or to unsubscribe, visit: > http://www.unidata.ucar.edu/mailing_lists/
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