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AIRS Level 2 RetQAFlag

  All Level 2 AIRS/AMSU/HSB products include a full swath data field named RetQAFlag. Users are strongly advised to use this 16-bit unsigned integer as an aid to data selection.

The best practice for selecting data to be included in scientific analyses is to avoid any field-of-view for which the RetQAFlag is non-zero.

All data are released to the public, however, the validation of retrieval algorithms and products has been carried out in this initial Level 2 release only in the case of those data that satisfy the following conditions
  • Low Latitude (with the latitude range 40 degree South to 40 degree North)
  • Ocean (land fraction in the AMSU field of view is less than 0.01)
  • Retrieved SST agrees with NCEP analysis to within 3.0 K
  • Sun glint avoided (glint distance greater than 200 km)
Only full retrieval results satisfying these conditions should be considered for scientific analyusis. Researchers can easily limit their selection of Level 2 data products to those satisfying these conditions bt using the included RetQAFlag. All fields-of-view whose RetQAFlag is zero satisfy these criteria.

The following table indentifies each bit currently being used in RetQAFlag.
  • Bits 0, 1, 2, 3, 4 are set in the case of a partial or rejected retrieval.
  • Bit 8 is set in this release version if a field-of-view is not an oceanic FOV located in the low latitude range, |lat| ≤ 40 degree.
  • Bit 9 is set if the retrieved SST deviaates from the NCEP forecast by more than 3 K.
BIT VALUE MEANING IF SET
0 1 MW-only retrieval stage rejected or not attempted
1 2 Initial Cloud Clearing rejected or not attempted
2 4 First Guess Regressing rejected or not attempted
3 8 Final Cloud Clearing Rejected or not attempted
4 16 Final Physical Retrieval rejected or not attempted
5 32 [currently spare, and set = 0]
6 64 [currently spare, and set = 0]
7 128 [currently spare, and set = 0]
8 256 Record Type Not Yet Validated
9 512 Ocean FOV rejected because ABS(Tsurf_ret - SST_NCEP_forecast) > 3 K
10 1024 [currently spare, and set = 0]
11 2048 [currently spare, and set = 0]
12 4096 [currently spare, and set = 0]
13 8192 [currently spare, and set = 0]
14 16384 [currently spare, and set = 0]
15 32768 [currently spare, and set = 0]


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  • Last updated: July 25, 2007 14:35:59 GMT