POTENTIAL FOR IMPROVED ATSR DUAL-VIEW SST RETRIEVAL

Recent validation studies have confirmed that the first along-track sc anning radiometer (ATSR) can retrieve sea surface temperature (SST) to an accuracy of 0.3K even in the presence of heavy atmospheric aerosol . However, using the standard (pre-launch) retrieval, this accuracy is achieved only when data from all three thermal channels (3.7, 11 and 12 mu m) are available; in the absence of 3.7 mu m data, retrieved SST s are subject to significant cold bias. As 3.7 mu m data are useful on ly for nighttime observations, and ATSR's 3.7 mu m channel failed in M ay 1992, only 11 and 12 mu m data informed SST derivation for most of the 1991-1996 mission. We demonstrate the potential for improvement in this retrieval, based on comparison of observed brightness temperatur es with precise SSTs derived using 3.7 mu m data. A reduction in globa l-mean cold bias from >0.6K to <0.1K is achieved, with standard deviat ion approximately halved. We also examine the treatment of optical pat hlength variation around the ATSR swath.