The importance of accurate skin temperature in assimilating radiances from satellite sounding instruments

An error analysis has been performed, which shows that skin temperature errors are important for sounding channels. An approach for estimating skin temperature and emissivity errors from the dependence of differences between observed and calculated radiances on surface-to-space transmittance is described. Estimates of emissivity and skin temperature error for the operational Met Office data assimilation system are presented as an example, and the implications are discussed, in terms of use of data over different surfaces and in different conditions (e.g., day/night). The results highlight the need for a better emissivity estimate over sea ice than that used at the Met Office and the inaccuracy of the land surface skin temperature that was derived from radiative flux balance at the surface.