Scanning infrared radiometer for measuring the air-sea temperature difference

We describe a vertically scanning infrared radiometer for measuring the air -sea temperature difference without disturbing the water skin layer. The ra diometer operates with a single wavelength channel that is 1.1 mum wide, ce ntered on 14.2 mum, on the short-wavelength edge of a CO2 atmospheric absor ption band. The resulting high atmospheric absorption enables calibration o f the horizontal-viewing signal with an in situ air-temperature sensor. The signal at all other scan angles is measured relative to that at the horizo ntal, providing a differential air-sea temperature measurement that is near ly independent of calibration offsets that can be a problem with independen t air- and water-temperature sensors. We show data measured on a ship in th e Tropical Western Pacific Ocean during July 1999, which exhibit important discrepancies from in situ data using bulk air- and water-temperature senso rs. These discrepancies illustrate important differences between bulk versu s skin water temperature. (C) 2001 Optical Society of America.