Development of an ocean surface wave climatology in support of continental shelf projects

This paper describes the development of an ocean surface wave climatology to support a typical continental shelf project such as the operations of an ROV, a mooring, or the erection of an offshore platform. The example used is designed for water depths from 33 to 610 meters, (100 to 2000 feet). The wave data development is described first. Second, a brief overview of the hydrodynamic modeling of the surface ship motions and the submerged ROV system based on the wave data. Lastly, a brief discussion of predicting the fatigue life of system components is also based on the wave climate data. Rather than base the scastate probability of occurrence on a published spread, such as Hogben and Lumb, (Lewis, 1990), which covers entire oceans, a new data set was developed for the project range of water depths. Long time series data was extracted from twenty eight NOAA/NDBC weather buoys that were located in the right water depths in the Atlantic and Pacific oceans. The summation includes 2.9 million hourly seastate readings spread over 326 data years. While the seastate percent occurrence numbers are not hugely different from typical ocean basin scale results, this method allowed the seas and swells to be resolved with surprising results. The data shows very significant differences from the most probable modal periods published for fully developed seas. The vast sample size insures that the environment is well represented. The fact that it is real world data, and not based on some mathematical abstraction such as "Fully Developed Seas", insures that the actual at sea conditions are modeled with reasonable accuracy. This technique is easily scalable to other projects and other use scenarios.