Thank you for your interesting question.
Most of GHRSST L3C subskin SSTs from AVHRR are produced by OSI SAF. For example, the https://podaac.jpl.nasa.gov/dataset/AVH ... F-L3C-v1.0
data. To understand why they are named as the subskin SST, please read the SST ATBD: http://www.osi-saf.org/lml/doc/osisaf_c ... eo_sst.pdf
. On page 19, it says "Since the coefficient of the SST algorithm are established using simulations from RTTOV radiative transfer model and de-biased against drifting buoys measurements (at a depth of 20 to 30 cm), the retrieved SST is considered to be the sub-skin SST."
Please let us know if you have more questions.