2022 CEOS International Thermal Infrared Radiometer Comparison. Part II: Field Comparison of Radiometers

Abstract

Abstract An international comparison of field-deployed radiometers for sea surface skin temperature (SSTskin) retrieval was conducted during two weeks in June 2022. The comparison comprised a laboratory comparison and a field comparison. The field comparison of the radiometers took place on the second week at a seaside pier on the south coast of England. Six thermal infrared radiometers were compared with each other while continuously viewing the closely adjacent surface of the sea from the end of the pier. This paper reports the results of this field comparison. All participants’ radiometers agreed with the reference value, evaluated as the simple mean of the participant-reported values, within the claimed uncertainties. The SSTskin variation during the 5-day period was within 3°C around 18.3°C, which is 2 times as large in range as in the previous comparison in 2016, while the mean of the difference from the reference value over the period evaluated for each participant was found to be within 0.07°C, which is a 2-times improvement on the previous results. During the comparison an insignificant but noticeable abrupt shift in measured value occurred in one of the radiometers, which could not have been detected without comparison with other instruments. This demonstrated the effectiveness of having long-term stable internal reference sources in the instrument, a feature this particular radiometer did not have. The combined results from the laboratory comparison and the field comparison contribute to improve confidence in the retrieved SSTskin.