Air-sea temperature differences measured with scanning radiometers during Nauru99

During June and July of 1999 the authors deployed a pair of scanning radiometers on the NOAA R/V RONALD H. BROWN (RHB) in the equatorial Pacific during the Nauru99 cruise, primarily in the vicinity of Nauru Island (~0° latitude, 166° E longitude). This pair of vertically scanning microwave and infrared radiomerers measures emission on the edge of a uniformly mixed atmospheric gas absorption line (0₂ for the mm-wave, and CO₂ for the IR). The horizontal atmospheric view is calibrated with a high-quality in-situ temperature sensor. The AC-coupled radiometer output voltage generates air-sea temperature differences from the voltage difference between the horizontal and downward-looking vertical views. Because the same calibration uncertainty applies to both air and water measurements, the differential temperature derived from the radiometer is more robust than what can be achieved by subtracting two independent sensor readings. Furthermore, the radiometric signals relate to the important skin temperature rather than the bulk water temperature