Evaluation of a coastal ocean model for Oahu, Hawaiʻi

Abstract

A coastal ocean model has been evaluated for Oahu, Hawaii. The three-dimensional hydrodynamic model used in this study is a semi-implicit version of ECOM that uses a z-level based coordinate system. The model has already been tuned and validated from the Eulerian viewpoint; however, it has not yet been validated from the Lagrangian perspective. Sea level records as well as temperature and salinity profiles were first used to validate the tuning of this model. This validation was performed using statistical parameters, such as correlation coefficients and standard deviations, to quantitatively characterize the model's capabilities. The simulated current structure was then qualitatively compared with the known current structure of Mamala Bay. This qualitative comparison focused on the circulation trends experienced at the headlands and in the bay throughout a daily tide cycle. After the model was successfully validated from the Eulerian perspective; its Lagrangian capabilities were then tested. The Lagrangian capabilities were tested by using the tuned model to virtually track drogues deployed on April 20, 2005 near the Sand Island outfall in Mamala Bay. The limited number of drogues deployed in this highly turbulent area restricted the ability to quantitatively analyze the Lagrangian results; therefore, these results were qualitatively analyzed to determine the model's Lagrangian capabilities. Successful validation of the model from both Eulerian and Lagrangian viewpoints demonstrate the "realism" of this coastal ocean model.