Retrievals of skin Sea-Surface Temperature (SST_skin) from the measurements of the Visible Infrared Imaging Radiometer Suite on the Suomi-National Polar-orbiting Partnership satellite are presented and discussed. The algorithms used to derive the SST_skin from the radiometric measurements are given in detail. A number of approaches to assess the accuracy and stability of the Visible Infrared Imaging Radiometer Suite (VIIRS) SST_skin retrievals are reported, and factors including latitude and season, and physical processes in the atmosphere and at the surface are discussed. We conclude that the Suomi National Polar-orbiting Partnership (S-NPP) VIIRS is capable of matching and improving upon the accuracies of SST_skin from the MODISs on Terra and Aqua, and that the VIIRS SST_skin fields have the potential to contribute to the extension of the satellite-derived Climate Data Records of SST into the future.

This paper presents physics improvements to the cool skin parameterization in the Coupled Ocean‐Atmosphere Response Experiment (COARE) bulk flux algorithm. The principal improvement is adopting a specification of the ocean side mixing profile that combines molecular and turbulent diffusivities via a form that allows turbulent dissipation to suppress turbulence near the interface. The turbulence is also scaled with the viscous friction velocity, since the stress input to waves is not realized continuously as turbulence at the interface but only intermittently at localized regions where the waves are breaking. Additional improvements include adopting a newer specification of the solar absorption profile in the ocean and incorporating the impacts of the rain sensible heat flux. The new parameterization is tuned to published observations of cool skin from a series of cruises and a recent publication of the turbo‐molecular mixing term deduced for observations of gas fluxes. Data from three recent ship‐based field programs, particularly the Propagation of Intraseasonal Oscillations in the Maritime Continent Region (PISTON) experiment, with radiometric sea surface and floating near‐surface temperature sensors as well as high‐quality air‐sea flux measurements were analyzed to evaluate the model. The improvements led to modest decreases in the nonsolar cool skin (∼16%) and in the solar heating contribution, both principally in light winds. The new model better reproduced mean nighttime cool skin amplitudes and was somewhat better than the previous COARE v3.6 model at reproducing the mean diurnal cycle. Overall, cool skin predictions for a large cruise database were reduced by ∼0.01°C.

We compared the results of an Optimal Estimation (OE) based approach for the retrieval of the skin sea surface temperature (SST_skin) with those of the traditional non-linear sea surface temperature (NLSST) algorithm. The retrievals were from radiance measurements in two infrared channels of the Moderate Resolution Imaging Spectroradiometer (MODIS) on the NASA satellite Aqua. The OE used a reduced state vector of SST and total column water vapor (TCWV). The SST and atmospheric profiles of temperature and humidity from ERA5 provided prior knowledge, and we made reasonable assumptions about the variance of these fields. An atmospheric radiative transfer model was used as the forward model to simulate the MODIS measurements. The performances of the retrieval approaches were assessed by comparison with in situ measurements. We found that the OESST reduces the satellite–in situ bias, but mostly for retrievals with an already small bias between in situ and the prior SST. The OE approach generally fails to improve the SST retrieval when that difference is large. In such cases, the NLSST often provides a better estimate of the SST than the OE. The OESST also underperforms NLSST in areas that include large horizontal SST gradients.