In Memoriam: Larry Hsu

Dr. Yuan-Huang Larry Hsu was an oceanographer in the Ocean Dynamics Branch of the Naval Research Laboratory, Stennis Space Center, MS. He passed away on July 30, 2010 at the age of 63. His research interests included the use of numerical models for coastal applications, wave and surf physics, and tidal dynamics.

         Dr. Yuan-Huang Larry Hsu

He was a member of the American Geophysical Union.

Larry received a B.S. in Mechanical Engineering from National Taiwan University in 1969, an M.S. in Mechanical Engineering from Duke University in 1971, and a Ph.D. in Marine Studies from the University of Delaware in 1981. For his dissertation, he investigated turbulent heat transfers in the atmospheric surface layer.

Larry began his career in the Navy with the Mapping, Charting, and Geodesy Branch in the Marine Geosciences Division of the Naval Ocean Research and Development Activity (NORDA) at the Stennis Space Center, MS in 1987. He worked at the Magnetic Observatory for several years investigating ocean processes using laser technology. He developed the Tidal Atlas Software (TAS), a PC-based application that allowed users to retrieve and display global tidal characteristics for any region or location. Graphical outputs included tidal data, cotidal and tidal height plots. The application was transitioned to the Naval Oceanographic Office in 1993. Larry served as an active member of the Joint Army/Navy Wave Prediction Group during the 1990s, and was the first Navy Chair of that collective.

Larry led the development of the NRL Swell Prediction model beginning in 1998. Collaborating with Dr. Bill O’Reilly (Scripps Institute of Oceanography), Paul Wittmann (Fleet Numerical Meteorological and Oceanography Center), and Dr. Robert Guza (Scripps Institute of Oceanography), he designed, tested, and implemented a ray tracing swell model using directional wave spectra from the Navy’s global wave model. The model was designed to propagate swell energy from source regions to forecast locations along great circle routes. The effect of island blocking was included using the Navy’s two-minute bathymetry database. The swell model was designed to generate forecasts of $10–20\text{days}$ . Swell forecasting from the system was provided to support the recovery of the Japanese fishing vessel Ehime Maru off the coast of Hawaii in 2001. The model was validated using data from the National Data Buoy Center.

Larry was recognized as a leading researcher in the field of surf forecasting. He worked with Dr. Marshall Earle, developer of the Navy Standard Surf Model (NSSM), implementing several physics-based improvements to the model, which he transitioned to the Naval Oceanographic Office. At that time, the one-dimensional NSSM was the primary software for US Navy operational surf forecasting. Outputs include surf zone width, longshore current, breaker type (spilling, plunging, or surging), and the Modified Surf Index (MSI) that characterizes overall surf conditions used in operational planning. Contributions to NSSM included the development of an improved longshore current model, code refinements from testing with hundreds of Beach Survey Chart profiles, streamlined and simplified user specified input, and more accurate refraction and shoaling computations. Utilizing video data from the Field Research Facility in Duck, North Carolina, video imagery was analyzed to improve calculations of surf zone width. The model was calibrated and validated with field and laboratory data.

More recently, he researched with Delft3D, a coastal hydrodynamic modeling system that includes the effects of waves, tides, and winds. Larry performed numerous validation studies with Delft3D utilizing data from Duck94 (barred beach), SandyDuck97, and the Nearshore Sediment Transport Study (steeper beach slope) in Santa Barbara, California. Validation studies showed that Delft3D was robust and accurate in predicting nearshore wave height and flows in a depth-averaged environment. Delft3D extended the capability of the 1-D NSSM by providing a two-dimensional surf prediction. Larry improved the functionality of Delft3D by providing two-dimensional surf parameters, such as modified surf index, longshore currents, breaker angle, and surf zone width. He transitioned Delft3D to the NAVO Coastal Prediction Division (NP2) in 2008.

Larry also worked with industry in the development of an Iridium-based directional wave buoy with an Acoustic Doppler Current Profiler. He collaborated with NRL colleagues and Dr. David Walker (SRI International) in the assimilation of buoy wave data in an adjoint wave model.

In addition to his research interests, Larry contributed to the Navy mission by providing numerical modeling support for several real-time exercises, including the NATO Exercise Strong Resolve (1998), in which refraction and shoaling coefficients were developed to produce accurate and efficient wave predictions near Sierra del Retin, Spain, and wave modeling support for AUVFEST 2001 in Mississippi Sound and the ONR Nearshore Canyon Experiment in 2003.

Several coastal researchers benefited from Larry’s insight and assistance throughout his career, including sponsorships for grants and promoting their work in the Navy/ONR community. Larry is remembered as a scientist with a kind and gentle nature, recognized and respected by his co-workers.

Survivors include his wife of $26\text{years}$ , Yu-Huey Sherry Hsu, a daughter Vicki, and a son Jeffrey, a college junior studying electrical engineering.