“The InfraRed Sea Surface Emissivity (IRSSE) model was developed for use in the Global Data Assimilation System (GDAS) at NCEP/EMC. Previously, the GDAS used an IRSSE model based on Masuda et al (1988).

“The Masuda model doesn’t account for the effect of enhanced emission due to reflection from the sea surface (only an issue for larger view angles) and the implementation was based on coarse spectral resolution emissivity data making its application to high resolution instruments, such as AIRS, problematic.

“The old IRSSE model has been upgraded to use sea surface emissivities derived via the Wu and Smith (1997) methodology as described in van Delst and Wu (2000).

“The emissivity spectra are computed assuming the infrared sensors are not polarised and using the data of Hale for the refractive index of water, Segelstein (1981) for the extinction coefficient, and Friedman (1969) for the salinitiy/chlorinity corrections.

“Instrument spectral response functions (SRFs) are used to reduce the emissivity spectra to instrument resolution. These are the quantities predicted by the IRSSE model.”