Improving Wave Hindcast Information for the Great Lakes

Abstract

The Wave Information Studies (WIS) at the U. S. Army Engineer Research and Development Center (ERDC) currently works on improving wave hindcast information for the Great Lakes. WIS has previously conducted the Great Lakes hindcast for 1956-1987. A recent update only covers Lake Michigan for 1988-1997. These hindcast studies were based on the deepwater wave modeling assumption that no shallow water effects were computed. Examining the previous hindcast results has shown notable bias in both wave height and period estimates. The bias is primarily caused by the poor quality of wind input information used in the hindcast. The present study is aimed at improving the wave hindcast using the newly generated wind field information that is considered to be more accurate and consistent in the long-term application. It is shown that to include shallow-water effects in the wave modeling is critical leading to accurate hindcast in the nearshore area. INTRODUCTION WIS has previously completed the Great Lakes hindcast for a 32-year period from 1956-1987 with the additional Lake Michigan hindcast from 1988-1997. A secondgeneration, time-dependent spectral model WISWAVE (Hubertz 1992) was applied in these hindcast studies using the deepwater wave assumption. The bathymetry effect that is important to the shallow-water wave transformation is not modeled in the hindcast. However, the bathymetry information is used to limit the wave height to 63 percent of the depth. The hindcast for each lake is conducted separately. The resolution of a wave model grid is 10 miles for all lakes in the 1956-1987 hindcast and 3 miles or equivalently 0.05 deg for Lake Michigan in the 1988-1997 hindcast. r Research hydraulic engineer. U.S. Army Engineer Research and Development Center, Coastal and Hydraulic Laboratory, 3909 Halls Ferry Road, Vicksburg, MS 39180, lihwa.lin @ erdc.usace.army.mil e Senior scientist. U.S. Army Engineer Research and Development Center, Coastal and Hydraulic Laboratory, 3909 Halls Ferry Road, Vicksburg, MS 39180, donald.t.resio@erdc.usace.army.mil