Edward P. Myers

Analysis of Factors Influencing Simulations of the 1993 Hokkaido Nansei-Oki and 1964 Alaska Tsunamis

The purpose of this paper is to examine factorsinfluencing numerical simulations of tsunamis, andtheir implications for hazard mitigation. We focus ona specific finite element hydrodynamic model, chosenfor its role in the systematic development ofinundation maps for regions threatened primarily byCascadia Subduction Zone (CSZ) tsunamis. However, inpart for generality and in part because of poorhistorical records for CSZ events, we discuss here theperformance of the model in the context of betterdocumented past events with epicenters locatedelsewhere: the July 12, 1993 Hokkaido Nansei-Oki andthe March 28, 1964 Alaska tsunamis. Our analysisincludes the influence of grid refinement,interactions between tides and tsunamis, artificialenergy loss, and numerical parameterization. We showthat while the ability exists to reproduce pastevents, limitations remain in the modeling processthat should be accounted for in translating modelingresults into information for tsunami mitigation andresponse.

Inversion for tides in the Eastern North Pacific Ocean

Abstract A regional model of tides in the Eastern North Pacific Ocean is developed through the use of inversion with two-dimensional finite element codes. Since global tide models are least accurate in coastal environments, modeling tides on a regional scale allows tidal propagation and interaction along the coast to be more accurately represented. In this respect, a regional model can act as a liaison between open ocean dynamics and physical processes more pertinent to coastal systems. The region of interest in this study extends from the Aleutian Islands to Southern California and includes deep ocean, continental shelf, and shallow water features. Boundary conditions are determined from nonlinear inversion of harmonic data from both shallow water and deep ocean tide gauges. Spatial patterns of amplitudes and phases from the model are examined for major constituents. Results are also compared to global tide models at selected stations.

Finite element modeling of the July 12, 1993 Hokkaido Nansei-Oki tsunami

A fault plane model and a finite element hydrodynamic model are applied to the simulation of the Hokkaido Nansei-Oki tsunami of July 12, 1993. The joint performance of the models is assessed based on the overall ability to reproduce observed tsunami waveforms and to preserve mass and energy during tsunami propagation. While a number of observed characteristics of the waveforms are satisfactorily reproduced (in particular, amplitudes and arrival times at tidal gauges relatively close to the source, and general patterns of energy concentration), others are only marginally so (notably, wave periods at the same gauges, and wave heights along Okushiri); differences between observations and simulations are traceable to both the fault plane and the hydrodynamic models. Nonnegligible losses of energy occur throughout the simulated tsunami propagation. These losses seem to be due to a combination of factors, including numerical damping and possible deficiencies of the shallow water equations in preserving energy.

A Forecast Circulation Model of the St. Johns River, Florida

This paper presents a nowcast/forecast hydrodynamic model of the St. John’s River, Florida. The model is one of the tools being developed for the pilot project of the Coastal Storms Initiative (CSI), an interdisciplinary program NOAA is implementing to enhance the tools and resources available to coastal communities during storm events. CIS provides a one-stop shopping approach for coastal managers to access information they need to make timely informed decisions. While CSI is developing new tools and collecting new data, it is also critical that it build upon existing resources. Such is the case with the circulation modeling of the river, as the St. Johns River Waste Management District (SJRWMD) had previously developed a well calibrated application of the Environmental Fluid Dynamics Code (EFDC) in the St. Johns River. To build upon this work, we ported their application to NOAA and integrated it into a real-time system for producing nowcasts and forecasts. Realtime data for winds, water levels, salinity and temperature are used to force the model nowcasts, and forecasts of wind and subtidal coastal water levels are used to drive the forecasts. The output is likewise made available in realtime on a website that will be accessible through the CSI home page. We are also developing the application of Eularian-Language Circulation (ELCIRC) model in the St. Johns River to examine the potential for simulating storm inundation in flood-prone areas of the watershed.

The St. Johns River Operational Forecast System: Evolution of an EFDC Model Application from Development to Operational Implementation

An operational forecast system using the Environmental Fluid Dynamics Code (EFDC) hydrodynamic model was implemented in the St. Johns River, Florida and has been running operationally at NOAA for six years. In this paper, we look back on the evolution of this system, including its development, testing, validation and operational implementation. As part of a program to examine water quality in the St. Johns River, the St. Johns River Water Management District (SJRWMD) developed this application of the EFDC hydrodynamic model to the lower St. Johns River. NOAA’s Coastal Storms Program facilitated the transition of this model to NOAA for evaluation and operational implementation as the St Johns River Operational Forecast System (SJROFS). Operational Forecast Systems (OFSs) run at NOAA’s National Ocean Service (NOS) and use the Coastal Ocean Modeling Framework (COMF) which employs standard procedures and formats for gathering inputs, formatting outputs and running the models. Since the SJRWMD application used the EFDC model, the initial step in porting their model into COMF was to adjust the output into the Cooperative Ocean/Atmosphere Research Data Service-compliant netCDF format that NOS supports. The EFDC simulations were set up to perform hourly nowcasts (a simulation over the previous one hour up until the present time) and four forecasts (extending 36 hours into the future) per day using the standard COMF scripts. The final step in the transition to operational implementation was to evaluate the performance of the model application against standard NOS skill assessment criteria. A software tool was developed to perform this skill assessment with models in the COMF environment, and the St. Johns River model results were subsequently analyzed using this tool for different simulation scenarios (tides only, hindcasts, operational nowcasts and forecasts). Skill assessment score tables were compiled for each location where observations were available using the software package, and these tables helped guide the best approach for transitioning the model to an operational environment. The SJROFS was made operational in October 2005, and comparisons between the model and available data are made publicly available on