Air-ocean-wave coupling of Hurricane Ivan (September 2004) in COAMPS-TC

Tropical cyclone (TC) air-ocean-wave interaction is examined using the state-of-the-art ESMF-based (Earth System Modeling Framework) tropical cyclone version of the Coupled Oceanic and Atmospheric Mesoscale Prediction System (COAMPS-TC) that was jointly developed by the Marine Meteorology and Oceanography Divisions of the Naval Research Laboratory. Both fully coupled and uncoupled atmosphere, ocean (Navy Coastal Ocean Model, NCOM), and wave (Simulation Waves Nearshore, SWAN) models were tested using the latest improvements in atmospheric and wave model physics, including a new sea spray module, a new wave input and dissipation parameterization (Babanin et al. 2010), and modified atmospheric and wave drag coefficients for high wind speeds based on observations.

This study examines intense Hurricane Ivan of September 2004 that traversed the Gulf of Mexico. Several oceanic and wave observational data sets, including Acoustic Doppler Current Profilers (ADCP), National Oceanic and Atmospheric Administration (NOAA) buoys, altimeter satellite data, and Scanning Radar Altimeter data (SRA), allow for a unique analysis of the ocean and wave models in COAMPS-TC. Primary results show that the Stokes' drift current (SDC) was approximately 10-20% of the total current near the surface of each shallow ADCP mooring during the greatest wind forcing period. The addition of the strong, hurricane-induced surface currents into SWAN lowered the significant wave heights when compared to the uncoupled model. Additionally, the modified atmospheric and wave physics yielded improved intensity forecasts for Hurricane Ivan when compared to observations.