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 - Mar 2010, ICOADS data was used instead of GTS.
Ship and buoy (drifters and moorings) data come from ICOADS, NCEP or FNMOC. Real time data are refreshed every 24hrs and ingested into iQuam with a latency of 4 hours on average. FNMOC, IMOS, HR-Drifter, ICOADS and ARGO data come with their own quality flags (QFs), which are preserved in the iQuam output files. In general, QFs from data sources are not used in the iQuam QC. Also, a blacklist QF based on the Copernicus Maritime Service (CMS) blacklist compiled by Meteo France is reported in iQuam output files but not used in iQuam QC. ARGO QFs are used to select the best quality near-surface data from above 10m depth, which are further subjected to the standard iQuam QC. ARGO data includes a greylist, which is is also reported in QFs but not used in QC. A blacklist for drifters, compiled by AOML, is also used. Again, this information is stored in QFs but not used in the QC.
iQuam QC is then performed and corresponding QFs 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. QCed in situ data, stored in self-described NetCDF format, are available via HTTP or FTP.
Currently, all processing of the previous month's data is completed by the 15th day of the following month.
The QC algorithm implemented in iQuam consists of
different steps of processing which can be categorized into
Inherited QC information - QC information from external sources, e.g. ICOADS QC, Argo QC and buoy blacklists - is reported in iQuam files but not used in setting up the iQuam QC.
In addition to some basic processing steps, the 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 existing Bayesian QC method [Lorenc and Hammon, 1988; Ingleby and Huddleston, 2007] with minor modifications. Details can be found in the following 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 maps, monthly QC/SST statistics, long-term time-series and individual platform statistics (track map, SST time series and performance history). In most cases, daily maps and statistics are available as well.
Interfaces are shown below.
The interface for platform monitoring:
In iQuam v2.10, the following in situ SST data types are included:
iQuam v2.10 data are in GDS compatible self-describing NetCDF 4 format. Refer to global and data layers attributes for more information. Suggested usage of the quality_level is:
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.
An example Python script is available from our ftp site. This script will download an iQuam data file and produce a scatter plot of the SSTs on a world map.
In situ SSTs sensors are mounted onboard different platforms and 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. Thus 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 and Chrome are supported. A minimum screen resolution of 960*720 is recommended to correctly display this web site. If there are any remaining issues, please contact us.
iQuam v2.10 files for the most recent month are updated every 24 hrs with an average latency of 4 hours. Data may be updated for several days after it is receieved. Data from the previous month are finalized on the 15th day of the following month.
fvxx.xnumbers in the iQuam data file names.
fvxx.x numbers in the iQuam data file names are an indication of the number of times a new version of the data has been produced,
after the nominal period of data gathering and processing has passed. During the current month, and for 4 days into the next month,
data files produced for that month are given a version number of
fv00.00. After that time, whenever a new data file is produced, the
version number is incremented by one, e.g. to
fv02.00, etc. Given that the file is processed at least one more time after the
nominal period, final files should have a version number of at least
fv01.00. Note that this code change was implemented in Apr 2017,
and prior to that all files were from reprocessed data and all fv's were set to
Currently the following upgrades in iQuam are being considered.
Dean Hinshaw: dean dot hinshaw at noaa dot gov
Haifeng Zhang: haifeng dot zhang at noaa dot gov
Alexander Ignatov: alex dot ignatov at noaa dot gov