DIRECTIONAL CHARACTERISTICS OF THE 1990-1999 WAVE INFORMATION STUDIES GULF OF MEXICO HINDCAST

gulfwavestudy
Page Navigation
1

Waterways Experiment Station

Vicksburg, MS

1. INTRODUCTION

Wave hindcast information is invaluable to coastal engineers, and validation of this hindcast

information is of utmost importance. The usual validation procedure is to compare hindcast information

with measured data at a coincident location. Wave height and period can be validated easily using linear

statistics but validation of wave direction is more complex since we are dealing with circular data. This

paper discusses statistical measures that give insight into the comparison of hindcasted mean wave

direction with measured mean wave direction. The statistical procedures described in this paper could be

applied to any of the other directional parameters available from the hindcast. Results are shown for the

recent 1990-1999 Wave Information Studies (WIS) Gulf of Mexico Level 3 Wave Hindcast produced at

the Engineer Research and Development Center's Coastal and Hydraulics Laboratory at the Waterways

Experiment Station in Vicksburg, Mississippi.

HINDCAST BACKGROUND INFORMATION

WIS has produced wave hindcast information for all the coastlines of the United States, and Gulf of

Mexico hindcast information has been created for 1956-1975 and for 1976-1995. A new hindcast has

recently been completed for 1990-1999 to take advantage of more Gulf of Mexico wind and wave

measurement locations, improved wind fields, and refinements in the wave hindcasting model,

WISWAVE. WISWAVE is a second generation spectral finite depth wave model which models the

physics of wave generation from a wind source function and uses a finite difference propagation scheme

to move wave energy on a set of rectangular grid points based on latitude and longitude. WISWAVE was

developed by Dr. Don Resio; and Resio (1981,1982), Resio and Tracy(1983) and Hubertz (1992)

describe the model. Quality wind fields are an essential component in the hindcasting process. The

1990-1999 wind fields were purchased from Oceanweather, Inc. These wind fields were created by

assimilating satellite information into the National Centers for Enviromental Prediction (NCEP) 6-hour

wind fields available from NOAA. Measured wind data and tropical storm information were assimilated

and blended to produce hourly wind fields. The final wind field product utilizes all available information

and expert meteorological analysis. The Gulf of Mexico hindcast included three levels, a 1-degree grid

that covered the Atlantic and Gulf, a Level 2 1/4-degree grid that covered the Gulf of Mexico, and a Level

3 1/12-degree grid that covered the entire Gulf coastal area. Each grid received spectral boundary

information from the previous level.

The Gulf hindcast information was compared to all available measurements in the area. Several

measurement devices in the Gulf were directional in the late 1990's and were used to validate the quality

of the hindcasted wave directional information. These directional measurement sites are shown in Figure

1. The grid in Figure 1 corresponds to the domain of the Level 3 Gulf grid. Table 1 lists relevant

information on these measurement sites.