Evaluation of three temperature profiles of a sublayer scheme to simulate SST diurnal cycle in a global ocean general circulation model

The diurnal cycle of sea surface temperature (SST) plays an important role in the upper ocean and climate system. One way to represents the diurnal variation of SST in Ocean General Circulation Models (OGCMs) with coarse vertical resolution is to parameterize the diurnal cycle of SST without considering detailed dynamic processes within the mixed layer. In this study, a diagnostic sublayer parameterization scheme following Schiller and Godfrey (2005) was incorporated into a global OGCM (NEMO), for the first time, to simulate the diurnal cycle of SST. Moreover, three different sublayer temperature profiles (constant, linear, and exponential) were evaluated. Comparison with satellite SST and mooring temperature data indicated that the parameterization scheme with an exponential temperature profile showed the most reasonable diurnal warming simulation results, significantly improving the probability of (from 1.7% with constant temperature profile to 13.4%) diurnal SST amplitude larger than 1.0 degrees C. Furthermore, the mean biases in each season were all reduced to less than 0.16 degrees C, in good agreement with observations.