iQuam was developed at NOAA Center for Satellite Application and Research (STAR). It performs three major functions, in near-real time:
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:
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:
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:
In iQuam2, eight in situ SST data types are included:
iQuam2 data are in GDS2 compatible self-describing NetCDF 4 format. Refer to global and data layers attributes for more information. Suggested usage of the quality_level are:
Note that all statistics presented on this website are based on the (quality_level == 5) condition. Please be advised that the quality control is only intended for sea surface temperatures. Other measurements have not been quality controlled.
All data can be directly accessed here.
In situ SSTs sensors are mounted onboard different platforms, maintained by different countries and agencies. Buoys remain unattended in a hostile environment for years, and ship records are subject to human errors. Additional errors occur during data transmission (to satellite and back to ground), processing and distribution via GTS. The quality of in situ SSTs is thus often suboptimal and non-uniform.
A small fraction of erroneous in situ measurements may significantly affect results of satellite Cal/Val. Non-QCed data cannot be used in Cal/Val, and removing 2-4% of bad reports significantly improves the validation statistics.
The QC practices adopted in the remote sensing community are overly simplistic, and far inferior to the more sophisticated, systematic, and well-developed procedures adopted in the meteorological and oceanographic communities. Moreover, the QC procedures are often inconsistent across various satellite SST groups, making their Cal/Val results difficult to compare.
NOAA is responsible for the maintenance and development of operational SST products from the polar and geostationary satellites. A near-real time in situ SST Quality Monitor (iQuam) was developed, using community advanced and consensus QC procedures and practices, to support Cal/Val efforts for a wide range of NOAA and GHRSST SST users.
Currently, mainstream browsers Firefox/Safari are supported. A minimum screen resolution 960*720 is recommended to correctly display this web site. If there is any remaining issue, please contact us.
iQuam files for the most recent month is updated every 12 hrs with a 2 hrs latency (i.e. 0600 and 1800 UTC). Data up to 5 days late in time may be updated.. Data of the month are finalized at the 5th day of the following month.
Xinjia Zhou: Xinjia dot Zhou at noaa dot gov
Feng Xu: Feng dot Xu at noaa dot gov
Alexander Ignatov: Alex dot Ignatov at noaa dot gov