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HOME > El Niño Monitoring > Description of Daily Sea Surface Analysis for Climate Monitoring and Predictions (COBE-SST version 1)

Description of Daily Sea Surface Analysis for Climate Monitoring and Predictions (COBE-SST version 1)

» Page : COBE-SST version 2

Notice: JMA has been providing COBE-SST2 (COBE-SST version 2) since December 2021. COBE-SST2 data are available on the NEAR-GOOS site. Please note that we explain about COBE-SST version 1 below, which is currently used for El Niño monitoring.


The method used for Sea Surface Temperature (SST) analysis in climate monitoring at JMA was updated to an approach based on in-situ observation in March 2006. For details of the analysis, see Ishii et al. (2005).

SST analysis involves a resolution of 1º latitude and 1º longitude. The east-west grid points run eastward from 0.5ºE to 0.5ºW, while the north-south grid points run northward from 89.5ºS to 89.5ºN. The daily analysis scheme is based on the optimum interpolation method, and the SST deviation from the normal for the previous day's analysis is multiplied by 0.95 for use as a first guess. The inputs of daily analysis are marine meteorological data for the seven-day period centered on the day in question. Observed data averaged daily in 1.5º x 1.5º boxes are used as super-observations to save processing time.

Bias correction for past SST observation reports was performed using the method of Folland and Parker (1995). Quality control for observation data is based on the of checking of ship tracks, dates and positions in reports, and any erroneous data are corrected automatically when marine meteorological data are compiled at JMA. Ship call signs with large data biases are automatically blacklisted in daily analysis based on the checking of such biases in the three-month period whose central month contains the day in question. In operational analysis, SSTs recorded over the past 30 days are re-analyzed sequentially every day with a delay of 31 days for the earliest analysis and 1 day for the latest in order to allow the utilization of delayed data and make the blacklist with the previous three months of data to be checked.

Information on sea ice concentration is used to estimate SSTs in the Arctic and Antarctic oceans.

Daily updated operational SST data are utilized for the following purposes along with historical data:

  1. Monitoring of equatorial Pacific SSTs, El Niño/La Niña evolution, Pacific Decadal Oscillation and global warming over 100 years,
  2. Input for the operational ocean data assimilation system (named MOVE/MRI.COM-G2) and historical oceanic analysis,
  3. Input for the Japanese 55-year Re-analysis (JRA-55) and JRA-55 real-time analysis.

The characteristics of the data are described in JMA (2006), which is available on Monthly Report on Climate System Separated Volume No.12.


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