Global Measurement of Sea Surface Temperature from Space: Some New Perspectives

Abstract

The measurement of global sea surface temperature (SST) from space is well established with 20 years of useful data already acquired, but the more stringent sampling requirements and the higher degree of accuracy now demanded for applications in both climate monitoring and operational oceanography are increasingly difficult to meet with the standard meteorological polar orbiting sensors that have been the basic sensors used for global SST mapping. The established methods and sensors for measuring SST, both in situ and in space, are reviewed, compared, and their major limitations are identified. Mention is made of phenomena which complicate an apparently simple measurement, including diurnal stratification, the presence of clouds and the contamination of the stratosphere by volcanic aerosols. Recent developments in remote sensing of SST are mentioned, noting the improved microwave sensors now becoming available, the calibrated infrared sensors planned for geostationary platforms, and weighing the benefits of merging these data. The conventional buoy-calibration of SST measurements from space is complicated by the variable thermal structure of the upper few metres of the ocean. The recent improvement of radiometers for ship deployment has led to better understanding of the thermal skin of the ocean which suggests a new approach for the validation of SST algorithms based on radiation transfer models. Finally, a future strategy is outlined for combining measurements from many types of sensor in order to achieve the required accuracy and sampling rate of SST data products, and to identify some of the remaining scientific challenges in this field.