NOAA Optimum Interpolation Sea Surface Temperature Analysis

Effective July 2020, the NOAA weekly and monthly Optimum Interpolation SST Analysis is maintained by the Climate Prediction Center.
Links to their ftp directories are included in the "Gridded Data via FTP" section below.


blue dotAnalysis Description and Recent Reanalysis
blue dot Plot Archives
blue dot Gridded Data via FTP
blue dot Climatology
blue dot Related Links
blue dot References
blue dot Contact Information
blue dot Frequently Asked Questions

Analysis Description and Recent Reanalysis

The optimum interpolation (OI) sea surface temperature (SST) analysis is produced weekly on a one-degree grid. The analysis uses in situ and satellite SSTs plus SSTs simulated by sea ice cover. Before the analysis is computed, the satellite data is adjusted for biases using the method of Reynolds (1988) and Reynolds and Marsico (1993). A description of the OI analysis can be found in Reynolds and Smith (1994). The bias correction improves the large scale accuracy of the OI.

In November 2001, the OI fields were recomputed for late 1981 onward. The new version will be referred to as OI.v2.

The most significant change for the OI.v2 is the improved simulation of SST obs from sea ice data following a technique developed at the UK Met Office. This change has reduced biases in the OI SST at higher latitudes. Also, the update and extension of COADS has provided us with improved ship data coverage through 1997, reducing the residual satellite biases in otherwise data sparse regions.  For more details, see Reynolds, et al (2002).

Plot Archives

The following links will take you to directories containing plots for weeks/months through June 2020.

tan dot Weekly Anomaly Plot Archive
tan dot Tropical Pacific Weekly Mean and Anomaly Plot Archive
tan dot Monthly Global SST Plot Archive
tan dot Monthly Global SST Anomaly Plot Archive

Gridded Data via FTP

The weekly and monthly fields through June 2020 are available in binary files in:
Documentation with sample source codes to read the data are available as README files in the above directories.

CPC's archive currently starts in February 2020 and is available at:
Differences during the overlap period are small and can be attributed to a few ship or buoy observations that made it into one analysis and not the other.>

The Data Support Section (DSS) of NCAR makes both available in ASCII at:
The NCAR archives may not be updated in real-time. So we have made recent data in NCAR's ascii format available on our server at:
for weekly and monthly fields respectively.

The NOAA Earth System Research Laboratory (ESRL) makes these data available in NETCDF at:


A climatology based on the OI.v2 Reanalysis fields was developed at the Climate Prediction Center using the method of Reynolds and Smith (1995) and Smith and Reynolds (1998). The latest version is available at:

Questions about the climatology or the above site should be directed to

Related Links

tan dot NOAA 1/4 degree Daily OI SST Analysis
tan dotNCDC's Extended Reconstructed Sea Surface Temperature (ERSST) Analysis Data


Reynolds, R.W., 1988: A real-time global sea surface temperature analysis. J. Climate, 1, 75-86.

Reynolds, R.W., 1993: Impact of Mount Pinatubo aerosols on satellite-derived sea surface temperatures. J. Climate, 6, 768-774.

Reynolds, R. W. and D. C. Marsico, 1993: An improved real-time global sea surface temperature analysis. J. Climate, 6, 114-119.

Reynolds, R. W. and T. M. Smith, 1994: Improved global sea surface temperature analyses. J. Climate, 7, 929-948.

Reynolds, R. W. and T. M. Smith, 1995: A high resolution global sea surface temperature climatology. J. Climate, 8, 1571-1583.

Smith, T. M. and R. W. Reynolds, 1998: A high resolution global sea surface temperature climatology for the 1961-90 base period. J. Climate, 11, 3320-3323.

Reynolds, R. W., N. A. Rayner, T. M. Smith, D. C. Stokes and W. Wang, 2002: An improved in situ and satellite SST analysis for climate. J. Climate, 15, 1609-1625.

Contact Information

Diane Stokes
(no longer works for the Environmental Modeling Center but may answer questions as time permits)

Please direct inquiries regarding CPC's updates to:
Bert Katz

Frequently Asked Questions

Click Here for FAQ