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20020607: GOES oversampling in element direction



>From: Darren Gallant <address@hidden>
>Organization: UCAR/JOSS
>Keywords: 200206051454.g55EsNJ12608 McIDAS script

Darren,

re: MAG= keywords for IMG* loads/copys of GOES-11 data.

>Thanks.

>Is there over sampling in the sounder data as well?

That is a good question.  A quick listing of the sounder data shows
that the resolution in the element direction is higher than that in the
line.  If this is caused by oversampling, it is not to the same extent
as for the imagery data:

IMGDISP GOES11/SNDR FORM=EXP
Image file directory listing for:GOES11/SNDR
 Pos Satellite/         Date       Time      Center      Res (km)   Image_Size
     sensor                                 Lat  Lon    Lat   Lon
 --- -------------  ------------  --------  ---- ----  ----- ----- ------------
 149  G-11 SND       7 JUN 02158  13:46:00    34   97
    Band: 1  14.7 um Stratosphere Temperature          13.51 10.39   192 x  292
    Band: 2  14.4 um Sounding;tropopause temperature   13.51 10.39   192 x  292
    Band: 3  14.1 um Sounding;upper-level temperature  13.51 10.39   192 x  292
    Band: 4  13.6 um Sounding;mid-level temperature    13.51 10.39   192 x  292
    Band: 5  13.4 um Sounding;low-level temperature    13.51 10.39   192 x  292
    Band: 6  12.7 um Sounding;total precip. water      13.51 10.39   192 x  292
    Band: 7  12.0 um Surface temperature and moisture  13.51 10.39   192 x  292
    Band: 8  11.0 um Surface temperature               13.51 10.39   192 x  292
    Band: 9   9.7 um Total Ozone                       13.51 10.39   192 x  292
    Band: 10  7.4 um Low-level moisture                13.51 10.39   192 x  292
    Band: 11  7.0 um Sounding;mid-level moisture       13.51 10.39   192 x  292
    Band: 12  6.5 um Sounding;upper-level moisture     13.51 10.39   192 x  292
    Band: 13  4.6 um Sounding;low-level temperature    13.51 10.39   192 x  292
    Band: 14  4.5 um Sounding;mid-level temperature    13.51 10.39   192 x  292
    Band: 15  4.4 um Sounding;upper-level temperature  13.51 10.39   192 x  292
    Band: 16  4.1 um Sounding;boundary layer           13.51 10.39   192 x  292
    Band: 17  4.0 um Surface Temperature               13.51 10.39   192 x  292
    Band: 18  3.7 um Temperature                       13.51 10.39   192 x  292

    Band: 19  0.70 um Clouds                           13.51 10.39   192 x  292
     proj:    0 created: 2002158 134706  memo: RT GVAR SOUNDER
     type:GVAR     cal type:RAW
     offsets:  data=    3328 navigation=  256 calibration= 2816 auxillary=    0
     doc length: 216   cal length:   0   lev length:  20 PREFIX= 236
     valcod:          0 zcor:  0 avg-smp: S
     start yyddd: 2002158  start time:134622  start scan:  349
     lcor: 3481  ecor:  7581  bytes per pixel: 2  ss: 77
     Resolution Factors (base=1):   Line=   10.0   Element=   10.0
IMGLIST: done

IMGLIST GOES11/CONUS FORM=EXP
Image file directory listing for:GOES11/CONUS
 Pos Satellite/         Date       Time      Center      Res (km)   Image_Size
     sensor                                 Lat  Lon    Lat   Lon
 --- -------------  ------------  --------  ---- ----  ----- ----- ------------
  45  G-11 IMG       7 JUN 02158  14:39:00    31   98
    Band: 1   0.65 um Visible - Cloud Cover             1.29  0.59  3620 x 8508
    Band: 2   3.9 um Night clouds; shortwave window     5.17  2.36   905 x 2127
    Band: 3   6.8 um Upper level water vapor            5.17  2.36   905 x 2127
    Band: 4  10.7 um Surface temp; longwave window      5.17  2.36   905 x 2127
    Band: 5  12.0 um Sea surface temp and water vapor   5.17  2.36   905 x 2127
     proj:    0 created: 2002158 143851  memo: RT GVAR
     type:GVAR     cal type:RAW
     offsets:  data=    3328 navigation=  256 calibration= 2816 auxillary=    0
     doc length: 228   cal length:   0   lev length:   0 PREFIX= 232
     valcod:  158143900 zcor:  0 avg-smp: N
     start yyddd: 2002158  start time:143851  start scan:  354
     lcor: 2829  ecor: 11581  bytes per pixel: 2  ss: 76
     Resolution Factors (base=1):   Line=    4.0   Element=    4.0
IMGLIST: done


As you can see, the oversampling of the imagery bands results in a resolution
ratio of about 2.1 (2.186 for VIS and 2.190 for the IR channels) while
the "oversampling" for the sounder bands results in a resolution ratio of
1.300.

In practice, this means that displaying the sounder bands with a MAG=1 -2
blow-down will not result in a round looking earth.

Tom


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