NOAA Optimum Interpolation (OI) SST V2

The Physical Sciences Laboratory has collected and made available netCDF files, the weekly, monthly NOAA OI SST V2 data and monthly long-term mean from NCEP (Y. Xue) based on the V2 data.

Weekly Data

The optimum interpolation (OI) sea surface temperature (SST) analysis is produced weekly on a one-degree grid. The analysis uses in situ and satellite SST's plus SST's 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).

The dates used in the netCDF files are the dates of the beginning of the 7-day average period. For the more recent period, 1990-present, the weeks are defined to be centered on Wednesday. During the period 1981-1989, the weeks are centered on Sunday.

The latitude/longitude values in the netCDF coordinate variables are the centers of the grid cells.

The ice field shows the weekly median ice concentration values input to the SST analysis. Ice concentration is stored as the percentage of area covered. For the ice fields, the land and coast have been set to the netCDF missing value. Note, the ice land mask is a function of the ice analysis and may change periodically.

The OI analysis is done over all ocean areas and the Great Lakes. There is no analysis over land. The land values are filled by a Cressman interpolation to produce a complete grid for possible interpolation to other grids. The ocean and land areas are defined by a land sea mask (the lsmask.nc file). Land values for sst do not necessarily coincide with land values from ice analysis.

Monthly Data

The NOAA OI.v2 SST monthly fields are derived by a linear interpolation of the weekly optimum interpolation (OI) version 2 fields to daily fields then averaging the daily values over a month. The monthly fields are in the same format and spatial resolution as the weekly fields.

The ice field shows the approximate monthly average of the ice concentration values input to the SST analysis. Ice concentration is stored as the percentage of area covered. For the ice fields, the land and coast grid cells have been set to the netCDF missing value.

Monthly Long-term mean Data

A climatology based on these fields was derived by Yan Xue of the NCEP Climate Prediction Center following the technique of Reynolds and Smith (1995) and Smith and Reynolds (1998). The climatologies are available here in the sst.ltm.*.nc files and include 1961-1990 and 1971-2000. See the references for details on how the climatologies were calculated.

1. Paper 1
2. Paper 2

For more information see https://www.nco.ncep.noaa.gov/pmb/products/sst/.

Usage Restrictions

• None

Caveats

• None.

Citation

• 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.

• Please note: If you acquire NOAA Optimum Interpolation (OI) SST V2 data products from PSL, we ask that you acknowledge us in your use of the data. This may be done by including text such as NOAA Optimum Interpolation (OI) SST V2 data provided by the NOAA PSL, Boulder, Colorado, USA, from their website at https://psl.noaa.gov in any documents or publications using these data. We would also appreciate receiving a copy of the relevant publications. This will help PSL to justify keeping the data freely available online in the future. Thank you!

Original Source

• NCEP: https://ftp.emc.ncep.noaa.gov/cmb/sst/oimonth_v2/
• NCEP: https://ftp.emc.ncep.noaa.gov/cmb/sst/oisst_v2/

References

• 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.