A Study of Six Operational Sea Surface Temperature Analyses

Abstract

This study results from recommendations made by a 1984 WMO Expert Committee on Ocean-Atmosphere Interaction Relevant to Long-Range Forecasting. The committee suggested that comparisons be carried out between monthly sea surface temperature (SST) analyses routinely made in several different countries in near real time. Emphasis was placed on the improvement of such analyses for use in operational long-range forecasting, especially for initializing dynamical long-range forecasting models. Six different monthly averaged SST analyses have been compared. The extent to which the analyses agree on several space scales and for regions covering the global oceans is shown, together with estimates of the magnitude of various types of errors. Independent estimates of SST obtained from expendable bathythermogmphs indicate that the monthly mean Meteorological Office (UKMO), Climate Analysis Center (CAC) in situ, and CAC blended analyses showed small differences (biases) from the expendable bathythermograph data. The differences were near to or below the margins of statistical significance over the Northern Hemisphere and the Southern Hemisphere tropics. Apparent negative biases in the analyses were noted, however, in the extratropical Southern Hemisphere. The authors finish with a discussion of recent improvements to the accuracy and scope of SST analyses for both long-range forecasting and climate studies. These improvements include an integrated analysis of ice limit, in situ and satellite SST data, and the developing use of optimum interpolation as a method of SST analysis.