Evaluation of Modeled Diurnal Warming Estimates for Use in Producing SST Analyses

Short abstract

The blending of SST retrievals from different times and representative depths in the generation of Level 4 SST analyses requires compensation for variability associated with processes like diurnal warming.  A version of the Kantha-Clayson one-dimensional turbulence closure model with wave effects has been modified to simulate diurnal warming at arbitrary times and depths based on forcing data obtained from global numerical weather prediction and wave models.  The model has been integrated into the NOAA NESDIS GOES-POES Blended SST analysis and shared with EUMETSAT.  The model performance using these forcing data, however, has not yet been thoroughly evaluated, particularly in instances of large diurnal warming which are of the greatest importance for application to SST analysis generation.

Here, we evaluate the model performance over four seasons using observations of diurnal warming derived from operational geosynchronous satellite SST retrievals.  The model is forced with 6-hourly data from the NOAA Global Forecast System (GFS) and Wave Watch III models and the simulated diurnal warming amplitudes are compared with estimates derived from the Meteosat-11, GOES-16, and Himawari-8 satellites.  Multiple model configurations and “tunable” parameters are evaluated to identify the best achievable performance.  Results from direct point-to-point comparisons and derived distributions of diurnal warming amplitudes provide a recommended model configuration and demonstrate that the model can yield realistic predictions with uncertainty levels sufficient for application to SST analyses.  The identified model configuration is also shown to produce accurate estimates of diurnal warming observed from multiple research cruises, lending additional confidence in the model performance.