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iQuam was developed at NOAA Center for Satellite Application and Research (STAR). It performs three major functions, in near-real time:

  • Quality controls (QC) in situ SSTs
  • Monitors QCed insitu SSTs online
  • Serves reformatted in situ SST data with quality level and flags appended

The real time processing is performed as follows

from Sep 1981 - Nov 2007, ICOADS data was used instead of GTS.

Ship and buoy (drifters and moorings) data come from ICOADS (Sep 1981-Nov 2007) or GTS (Dec 2007-pr) data. Real time NCEP GTS are refreshed every 12hrs in injected into iQuam with a 2hr latency. ARGO data on US GODAE/GDAC (link) are refreshed .. and ingested with .. latency. ICOADS and ARGO data come with their own quality flags (QFs) and quality indicators (QI), which are preserved in iQuam output files. ICOADS QFs are not used in iQuam QC. Also OSI SAF "black list" QF is reported in iQuam output files but not used in iQuam QC. Analyses of the relative merit of iQuam and ICOADS and OI SAF black list QCs is currently underway and their results will be reported elsewhere. On the other hand, ARGO QFs are used to select the best quality near-surface data from 3-7m depth, which are further subject to the standard iQuam QC.

iQuam QC is then performed and corresponding QFs/QIs are appended (but not applied) to in situ data. All in situ data are preserved in iQuam files, and no data excluded based on iQuam or external QFs/QIs. QCed in situ data in self-described netcdf format are available via HTTP or FTP.

Currently, all processing of the previous month data is complete by the 5th day of the following month.

QC algorithm implemented in iQuam consists of different steps of prcessing which can be categorized into five groups:

  • Prescreening - Processing which precedes QC checks and is aimed at resolving known data-specific historical problems (e.g., removal of duplicates and wrongly formatted data).
  • Plausibility check - Analyzes individual fields in the data records and relationships between them to verify their plausibility (e.g., geolocation check).
  • Internal consistency check - Checks different measurements from the same platform for internal consistency (e.g., tracking and SST spike checks).
  • Mutual consistency check - Checks nearby measurements from different platforms for consistency (also known as 'cross-platform' or 'buddy check').
  • External consistency check - Checks in situ SST for consistency with reference (first-guess) field (also called 'reference check' or 'background check')
  • Inherited QC information - Checks with QC information from external sources, e.g. ICOADS QC, Argo QC and CMS buoy balcklist

In addition to some basic processing steps, 5 major steps are duplicate removal (DR), platform track check (TC), SST spike check (SC), reference check (RC) and cross-platform check (XC). Algorithms for the reference check and the cross-platform check are employed from the currently existed Bayesian QC method [Lorenc and Hammon, 1988; Ingleby and Huddleston, 2007] with minor modifications. Details can be found in publications:

  • Xu, F. and A. Ignatov, 2013: in situ SST quality monitor (iQuam), JTECH, submitted. download
  • Ingleby, B. and M. Huddleston, 2007: Quality control of ocean temperature and salinity profiles - historical and real-time data, J Marine Systems, 65, 158-175.
  • Lorenc, A.C. and O. Hammon, 1988: Objective quality control of observations using Bayesian methods. Theory, and a practical implementation. Q. J. R. Meteorol. Soc. 114, 515-543.

Flowchart of QC algorithm is as follows.

Monitoring of statistics of both QC and SST anomalies are also provided in iQuam. It includes monthly global map, monthly QC/SST statistics, long-term time-series and individual platform statistics (track map, SST time series and performance history).

Interfaces are shown below.

Specifically, interface for platform monitoring:

Time series of monthly statistics (SD of Pathfinder minus in situ SST) before (left) and after (right) QC: