Description of the OI.v2 Monthly SST 1971-2000 Climatology

A new sea surface temperature (SST) climatology for the 1971-2000 base period was constructed using the method of Reynolds and Smith (1995). The new climatology was built from two intermediate climatologies: a 2 degree SST climatology developed from in situ data for the period 1971-2000, and a 1 degree SST climatology for the period 1982-2000 derived from the second version optimum interpolation (OI.v2) SST analysis. The OI.v2 is a major improvement over the original OI analysis (OI.v1) at high latitudes due to a new ice algorithm (Reynolds et. al. 2001). The OI.v2 was put into operation at the Climate Prediction Center in August 2001.

The changes in the climatology are caused by the changes in the base period as well as the changes in the OI analysis. The figures at http://www.cpc.noaa.gov/products/predictions/30day/SSTs/sst_clim.html show the new SST climatology (column 1), the changes of climatology due to the changes in the base period (column 2), and the changes of climatology due to the changes in the OI analysis (column 3). In the tropics and subtropics, the changes in the climatology are largely due to the changes in the base period, and are generally small with absolute differences usually less than 0.2C (column 2 and column 3). However, in high latitudes the changes in climatology are due to the changes in the OI analysis alone. This is because there are insufficient in situ observations in high latitudes prior to 1982, and the climatology is based on the OI analysis alone (1982-2000). It is seen that the changes of climatology due to the changes in the OI analysis often exceed 1C (third column).

The OI.v2 can be downloaded from ftp://ftp.ncep.noaa.gov/pub/cmb/sst/oisst_v2, and the SST climatology derived with OI.v2 for the 1971-2000 and 1961-1990 base periods can be downloaded from ftp://ftp.ncep.noaa.gov/pub/cpc/wd52yx/sstclim.

Questions can be sent to Yan Xue at yan.xue@noaa.gov.