Advances towards the operational validation of satellite sea surface skin temperature observations

Deploying infrared radiometers at sea is difficult due to the harsh environmental conditions often encountered and high costs associated with many sea-going radiometer systems. This has prevented the operational collection of a global in situ sea surface skin temperature (SSST) data set forcing many satellite validation exercises to rely on subsurface “bulk” sea surface temperature (BSST) observations. We describe a low cost infrared radiometer system that can be used within a ship of opportunity program (SOP) to generate a high quality and geographically widespread SSST data set suitable for the operational validation of satellite SSST observations. The Ship of Opportunity Sea Surface Temperature Radiometer 1 (SOSSTR-1) uses two Tasco Ltd. THI-500L radiometers mounted in a robust environmentally protected case which provide near continuous sea and sky brightness temperature measurements. Each radiometer is regularly calibrated by viewing two precision blackbody cavities maintained at different temperatures. The enclosure is held at a positive pressure to minimize contamination of the radiometer fore-optics by water ingress through a single aperture. A time series of SOSSTR observations from the Atlantic Meridional Transect-5 experiment and post-cruise calibration data are used to demonstrate operational capabilities of the SOSSTR radiometer. The instrument is able to measure SSST to an accuracy of ~0.1 K and can compensate for contamination of the instrument fore-optics once surface water has evaporated