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| | Important notice to
Argo users (pressure offset errors, 2nd notice):
This is to provide an update to the earlier notice (see
http://www-argo.ucsd.edu/Acpres_offset.html), with regard to progress in
correcting pressure offset errors.
- Pressure offset errors in WHOI/FSI Argo float
profiles include a subset (a) that can be corrected exactly using automated
procedures and a subset (b) that requires expert examination to produce an
approximate correction.
- Profiles in subset (a) have now been corrected,
and replacement of GDAC files for these profiles will be completed by 30
September. Procedures for real-time correction of these profiles will be
in place by 31 October. When this is implemented, instruments presently
“greylisted” due to the offset error will be delisted, meaning the
profiles will be available on the GTS.
- Profiles in subset (b) are undergoing expert
examination and the files are being replaced on the GDAC as they are
completed. Errors are noted in the files corresponding to the
uncertainty in the pressure correction. Since these profiles cannot be
corrected automatically, the corresponding instruments continue to be
greylisted (i.e. profiles are not on the GTS).
- While studying the pressure offset errors,
a related problem was discovered in a group of WHOI/SBE profiles. Reported
pressures from these instruments corresponded to the bottom pressure of bins
rather than to the mid-bin pressure. This ½ bin pressure offset error is
generally less than for the profiles noted in (1) above. For the affected
WHOI/SBE instruments, all profiles have now been corrected and will be
replaced on the GDACs by September 30. The real-time data stream for these
instruments has been corrected (as of 16 August). These instruments are not
"greylisted".
WMO ID numbers for the affected instruments in each of the
groups discussed above will be posted on this notice (i.e. at
http://www-argo.ucsd.edu/Acpres_offset_2.html), in the near future.
The Argo project will continue to improve procedures for
detection and correction of data quality problems, and Argo endeavors to provide
data of highest possible quality. Users should note that near real-time data are
subject only to automated quality checking, and the best quality data for
climate research applications are available only in delayed-mode (“D” files).
Users can assist by reporting any data quality problems to
support@argo.net and to
the AST co-chairs if the problems persist.
Dean Roemmich and Howard Freeland, on behalf of the international Argo
Steering Team
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