MARINE SURFACE-TEMPERATURE - OBSERVED VARIATIONS AND DATA REQUIREMENTS

Measurements of temperature at the ocean surface are an indispensible part of the Global Climate Observing System (GCOS). We describe the va rying coverage of these measurements from the mid-nineteenth century t hrough to the present era of satellite data, along with ongoing attemp ts to augment the available digitized data base. We next survey attemp ts to remove systematic biases from both sea surface temperature (SST) and marine air temperature (MAT) data and to combine in situ and sate llite SSTs in a consistent manner. We also describe new or planned geo graphically complete climatologies of SST and night MAT for 1961-90. T hese are expected to be more reliable than existing climatologies in t he Southern Ocean and other sparsely-observed areas. The new SST clima tology has been used in the construction of an improved geographically -complete data set of sea ice and SST: the techniques used are briefly reviewed, as are other methods of analysis and assessment of worldwid e SST. We present global and regional time series of anomalies (i.e. d eviations from reference climatology) of SST and night MAT for 1856 to 1994 constructed using the most complete data and best-estimate bias- corrections hitherto available. These series are compared with earlier published series, and are validated by means of comparisons with anom alies of air temperature from coastal and island stations. The sensiti vity of the time series to imperfect coverage is assessed by means of frozen grid experiments. The results underscore the need for ongoing d evelopment of SST and MAT data bases within GCOS for the detection of climatic change, and for improved methods of analysis to optimally iso late the signals from incomplete data.