Comparison of the Observed Mixed Layer Depth in the Lee of the Hawaiian Island to the Modeled Mixed Layer Depth of the Regional Navy Coastal Ocean Model

This study evaluates the ability of the Hawaii Regional Navy Coastal Ocean Model to accurately predict the depth of the surface mixed layer in the lee of the Hawaiian Islands. Accurately modeling the depth of the surface mixed layer in this complex wake island environment is important to naval operations because the area hosts numerous training exercises. The simulated data were compared to CTD data collected from sea gliders, and tests for correlation were conducted. For mixed layer depths that did show correlation, match-paired t tests were used to determine the significance of the correlations. It was determined that the Hawaii Regional Navy Coastal Ocean Model has difficulty accurately predicting the depth of the surface mixed layer. It was also determined that the model has difficulty with unusual oceanographic features such as mode water eddies. These features are too uncommon and short-lived to be depicted in the climatology data. The climatology data are a major component of the synthetic profiles that the model generates, and these profiles tend to smooth out the unusual subsurface isothermal layer. List of Abbreviations BT - bathythermographs CCE - cold core eddy COAMPS - Coupled Ocean/Atmosphere Mesoscale Prediction System CTD - conductivity, temperature, and depth GDEM - Generalized Digital Environmental Model IR - infrared MLD - mixed layer depth MODAS - Modular Ocean Data Assimilation System MOODS - Master Oceanographic Observation Dataset NCODA - Navy Coupled Ocean Data Assimilation NCOM1 - Hawaii Regional Navy Coastal Ocean Model with in situ assimilation NCOM2 - Hawaii Regional Navy Coastal Ocean Model without in situ assimilation PAVE - Profile Analysis and Visualization Environment SSHa - sea surface height anomaly derived from altimetry SST - sea surface temperature WCE - warm core eddy