|Kaplan's SST Data Set|
|Variable(s)||Sea Surface Temperature|
|Land or Ocean||Ocean|
|Current Period of Record||1856-Current|
|Resolution||Monthly, Global, 5o x 5o|
|Description:||Optimal statistical analysis for historical datasets: 136 years of Global Sea Surface Temperatures|
|Reference:||Kaplan, A., M. Cane, Y. Kushnir, A. Clement, M. Blumenthal, and B. Rajagopalan, Analyses of global sea surface temperature 1856-1991, Journal of Geophysical Research, 103, 18,567-18,589, 1998.|
|Data Set Location:||
Original data set, 1856-1991|
Extended data set, 1856-Current
|Technical Overview||Expert User Guidance||Relevant Articles||Coverage Maps|
analysis (1856-1991) is described below by Alexey Kaplan in the
Expert User Guidance
section of this page. Dr. Kaplan explains that, due to demand, there exists a current
version of the dataset, referred to as the
Extended SST dataset (1856-Current).
For 1856-1981 this is the analysis of Kaplan et al.  which uses optimal estimation in the space of 80 empirical orthogonal functions (EOFs) in order to interpolate ship observations of the U.K. Met Office database [Parker et al. 1994]. The data after 1981 reperesents the projection of the NCEP OI analysis (which combines ship observations with remote sensing data) by Reynolds and Smith  on the same set of 80 EOFs as used in Kaplan et al.  in order to provide enhanced data quality of the former in the spatial resolution of the latter.
IMPORTANT: If you do not care about statistical homogeneity of the long (starting pre-1981) SST records, and just need SST data after 1981, please use the original NCEP OI data. It is much better (1x1 degree resolution weekly based) SST analysis, which was degraded in the present product.
Kaplan SST Description
This analysis uses present-day temperature patterns to enhance the meager data available in the past. Reduced Space Optimal Estimation has been applied to the global sea surface temperature (SST) record MOHSST5 (ATLAS7) from the U.K. Meteorological Office to produce 136 years of analyzed global SST anomalies (with regards to normals of 1951-1980) , where data gaps are removed and sampling errors are diminished. The results of this analysis are available as a dataset, including an interactive viewer and downloadable data files.
For more detailed information concerning this data set, please refer to this IRI/LDEO site.
|Expert User Guidance|
Least squares procedures of optimal estimation, when applied to gappy and erratic data, result in the solutions which predominantly project onto the most energetic patterns of a priori error covariance. This property of the solution allows to combine the classical least squares technique with the approach of a space reduction in order to develop a computationally effective procedure of objective analysis for observed historical climate data. (Such data are characterized by comparatively precise observations and good coverage in the last few decades, and poor observational coverage prior.) An important aspect of our approach is that it also produces verifiable error bars for analyzed values. For details of the technique see Kaplan et al. 1997, for a simple qualitative introduction see Kaplan et al. 2001.
Here we applied the reduced space optimal smoother technique to the U.K. Meteorological Office observational data set of historical sea surface temperatures (SST) (Bottomley et al 1990; Parker et al 1994). The primary difference between the British data set and the COADS SST is that the former was corrected for the systematic biases in bucket measurements of SST before 1940s (Folland and Parker, 1995). The details of our analysis ( http://ingrid.ldgo.columbia.edu/SOURCES/.KAPLAN/.RSA_MOHSST5.cuf/.OS/.ssta/) and its verification are given in Kaplan et al. 1998, but there are a few points I'd like to make here:
Bottomley, M., C.K. Folland, J. Hsiung, R.E. Newell, and D.E. Parker, Global Ocean Surface Temperature Atlas, Her Majesty's Stn. Off., Norwich, England, 1990. Folland, C.K., and D.E. Parker, Correction of instrumental biases in historical sea surface temperature data, Q. J. R. Meteorol. Soc., 121, 319-367, 1995.
Hurrell, J.W., and K.E. Trenberth, 1999: Global sea surface temperature analyses: multiple problems and their implications for climate analysis, modeling, and reanalysis. Bull. Amer. Meteor. Soc., 80, 2661-2678.
Kaplan A., M.A. Cane, and Y. Kushnir, 2001: Reduced space approach to the optimal analysis interpolation of historical marine observations: Accomplishments, difficulties, and prospects, WMO Guide to the Applications of Marine Climatology, World Meteorological Organization, Geneva, Switzerland, in press; available at http://rainbow.ldeo.columbia.edu/~alexeyk/CLIMAR99/wmogr.ps
Kaplan, A., M. Cane, Y. Kushnir, A. Clement, M. Blumenthal, and B. Rajagopalan, Analyses of global sea surface temperature 1856-1991, Journal of Geophysical Research, 103, 18,567-18,589, 1998.
Kaplan, A., Y. Kushnir, M. Cane, and M. Blumenthal, Reduced space optimal analysis for historical datasets: 136 years of Atlantic sea surface temperatures, Journal of Geophysical Research, 102, 27,835--27,860, 1997.
Parker, D.E., P.D. Jones, C.K. Folland, and A. Bevan, Interdecadal changes of surface temperature since the late nineteenth century, J. Geophys. Res., 99, 14,373-14,399, 1994.
Click on the links below to view data coverage maps for a particular time period. Percentage of non-missing data per time period is plotted. Coverage is consistent throughout the period of record.