3.4
Regional wave modeling in the Southern California bight
Nicholas E. Graham, SIO/Univ. Of California and Hydrologic Research Center, La Jolla, CA; and S. V. Taylor
The outer waters of the Southern California Bight are well known for episodes of large fair weather northwesterly wind-waves during late spring and summer. These waves, occasionally reaching 4-5 meters, frequently occur when the prevailing northwesterly coastal swell interacts with topographically enhanced northwesterly flow around Point Conception and the Channel Islands, and the resulting wave field is characterized by sharp spatial gradients in height due to sheltering and spatial variability in the wind field. Such waves are of obvious concern for offshore operations and boating safety, and are locally important for sediment transport. We present results from simulations with a nested implementation of the National Centers for Environmental Predictions (NCEP) Ocean Modeling Branch (OMB) WAVEWATCH-III model for the Southern California Bight. The outer nest of the model covers the full Pacific Ocean from 100°E to 68°W and from 66°S to 60.5°N at a resolution of 1.5° latitude x 2.0° longitude. A middle nest covers 130-116° W and 30-39°N with a resolution of 0.25°. The inner nest covers 32-35°N and 122-117°W with 5-minute resolution. For the simulations described here the outer two domains of the wave model are driven with winds from the NCEP Global Forecast System (GFS) as processed by OMB. The inner domain is driven with winds from the 12 kilometer resolution implementation of the NCEP ETA regional model. The simulations will cover March-July of 2003, thus covering much of the important spring and summer seasons.
Preliminary simulations show that driving the regional wave model with ETA-12 winds and boundary conditions from the 0.25° model can substantially improve the simulation of waves in the Southern California Bight during periods when winds are moderate to strong. We will describe the basic configuration of the nested model along w comparisons between buoy measurements and wave model results, with emphasis on understanding particular aspects of model/data agreement and disagreement. A companion paper will compare winds from the ETA 12 model and regional observations with respect to the performance of the regional wave model performance.
Session 3, Waves
Thursday, 7 August 2003, 8:00 AM-9:40 AM
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