Finding NOMAD : an examination of the impacts of changing wave systems on long-term wave measurements

Bouchard, Richard H. and Jensen, Robert E. and Montalvo, Sofia and Kamranzad, Bahareh (2018) Finding NOMAD : an examination of the impacts of changing wave systems on long-term wave measurements. In: 2018 Ocean Sciences Meeting, 2018-02-11 - 2018-02-16.

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Abstract

The National Oceanic and Atmospheric Administration (NOAA) presently holds more than 30,000 months of data from moored buoys operated by the National Data Buoy Center (NDBC). These data span 40 years and much of the data includes wave measurements. This dataset could provide a rich source of wave data for detecting change, identifying trends, and understanding variability of the waves that affect storminess, future ship design, and renewable energy projections; however, recent studies indicate that changes in the buoy hull and wave processing can obscure or induce artificial changes in the long-term wave records. To enhance the utility of these long-term wave measurements, we made use of two years of data collected during the FLOSSIE Project. The US Army Corps of Engineers, Coastal and Hydraulics Laboratory sponsored the Project to compare older wave systems with newer waves systems. The Project deployed a Navy Oceanographic Meteorological Automatic Device (NOMAD) buoy, with an older NDBC wave processing system, in the vicinity of a different type of NDBC hull (3-m discus) hosting a newer NDBC wave processing system. We analyzed the two years of data and examined the differences between the two systems for wave heights and periods and the combined parameters, steepness (ship response) and wave power (renewable energy). We simulated the changing of wave systems by creating and analyzing datasets consisting of the first year of the older system followed by a year of the newer system. While the two buoys show similar trends over the two-year period, the simulated-change datasets provided different trends and projections. To assist users in identifying NOMAD hulls in the archives, NDBC has compiled and will publish a comprehensive list of NOMAD deployments. We also describe on-going and follow-on work to determine methods to correct and homogenize the data.

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