Global differences between skin and bulk sea surface temperatures



Infrared satellite imagery provides one of the best means of mapping changes in global sea surface temperature (SST). A series of workshops [Hilland et al., 1985], held to compare the various methods of remotely sensing SST, concluded that of the presently available systems, the Advanced Very High Resolution Radiometer (AVHRR), carried on National Oceanic and Atmospheric Administration (NOAA) polar-orbiting weather satellites, yielded the smallest rms error when compared with ship and buoy in situ data. The widely used Multi Channel SST (MCSST) method, described by McClain et al. [1983], was used to calibrate the AVHRR SST for this workshop intercomparison. This method uses the differences between the radiances of the two AVHRR thermal infrared channels to correct for atmospheric signal attenuation due primarily to water vapor absorption. To provide absolute temperature calibration, the MCSST coefficients are derived by matching the AVHRR observations with simultaneous SSTs measured in situ by freely drifting ocean buoys [McClain et al., 1985]. These drifting buoys typically measure the ocean temperature 0.5–1 m below the sea surface.