High latitude sea surface skin temperature from the Saildrone uncrewed surface vehicles deployed in 2019

Saildrone, as one of the most capable uncrewed surface vehicles, carries a suite of meteorological and oceanographic instruments for long-duration cruises. From 15th May to 11th October 2019, two NASA-funded Saildrones, SD-1036 and SD-1037, made a 150-day round-trip cruise from Dutch Harbor, Alaska, into the Arctic Ocean. Both were equipped with a pair of IR pyrometers on the deck at 0.8 m height for the sea surface skin temperature (SSTskin) retrieval, viewing the sea surface and the sky at the same nadir angle and zenith angles. The pyrometers were manufactured by Heitronics Inc., the sea-viewing sensor was a CT15.10 while the sky-viewing sensor was a CT09.10. After the deployments, the CT15 calibration was tested in the University of Miami Rosenstiel School laboratory using SI-traceable blackbody calibrator, and also by Wintronics, the US agent of Heitronics Inc. The performance of CT15 was much better than the stated accuracy in the manufacturer's specifications. The uncertainty of Saildrone-derived SSTskin is ~0.12 K and the systematic error is insignificant. Therefore, the SSTskin data from SD-1036 and SD-1037 are sufficiently accurate to be used in the validation of satellite SSTskin retrievals and other studies of sea surface and air-sea interaction at high latitudes.