Sea surface temperature measurements with AIRS: RTG.SST comparison

The comparison of global sea surface skin temperatures derived from cloud-free AIRS super window channel at 2616 cm-1 (sst2616) with the Real-Time Global Sea Surface Temperature (RTG.SST) for September 2002 shows a surprisingly small standard deviation of 0.44 K; however, sst2616 is colder than the RTG.SST by 0.67 K. About 0.35 K of the cold bias is due the expected bulk-skin gradient and the effect of using the day/night average RTG.SST for a nighttime comparison. The other 0.32 K is due to an absorbing layer in the atmosphere. There are large areas of the oceans where this absorbing layer is absent, and other areas where it is as large at 1.5 K. The layers persist regionally on a months timescale and might be related to some form of aerosol or marine haze. A correlation with major weather events, like the Monsoon season in the Indian ocean and, possibly, El Nino events is suspected, but has not been demonstrated. AIRS was lauched into polar orbit on the EOS Aqua spacecraft on May 4, 2002.