Comparison of Skin Sea Surface Temperature Parameterizations Applied to a 3-D Ocean Circulation Model in a Coastal Environment

Observations of the sea surface temperature (SST) in the thin layer approximately 1 mm below the sea surface often reveal a non-negligible departure from (bulk) SST measurements at lower depths (e.g. 1 m) within the ocean mixed layer. This skin layer SST (SSST) is proposed to develop in response to light wind conditions and turbulent heat flux from the ocean surface to the atmosphere, often resulting in a cooling from the bulk SST that can occasionally exceed 1°C. Ocean circulation models and coupled atmosphere-ocean model systems, however, cannot resolve this thin skin layer, meaning that SSST must be parameterized by adding a correction to the modeled SST. A parameterization for SSST is particularly important for numerical models of the atmosphere that rely upon an SST to estimate surface turbulent scalar flux and surface layer profiles. Here we evaluate three parameterizations recently implemented into the Navy Coastal Ocean Model (NCOM): Saunders (1967) [S67], Soloviev and Schluessel (1994) and Zeng and Beljaars (2005) [ZB05]. Additionally, we evaluate a modification to S67 that includes solar radiation, following Fairall et al. (1996). The ZB05 scheme includes a near-surface warm layer that serves to decrease the magnitude of surface cooling. The evaluation here includes tests using different warm layer depths (3 m and 5 m) in the ZB05 scheme. We perform an inter-comparison and validation of these parameterizations using the measurements of SST and SSST from a research vessel operating off-shore of the U.S. East Coast over 26 days in the autumn of 2015 as part of the CASPER-East field campaign. During this period, there were multiple events where observed SSST is at least 1°C cooler than SST in various regions along the ship track, and multiple events of large SSST-SST difference outside the verification area with varied response by the parameterizations. The ZB05 scheme yields several periods of warm skin conditions during the field campaign (SSST warmer than SST), some corresponding to warm periods of observed warm skin conditions.