Performance of the first year of the completed US operational deep-sea tsunameter network

Abstract

In March 2008, the National Oceanic and Atmospheric Administration's (NOAA) National Data Buoy Center (NDBC) completed the deployment of the full 39-station network of deep-sea tsunameters bolstering the U.S. tsunami warning system. This vast network of 39 stations provides coastal communities in the Pacific, Atlantic, Caribbean and the Gulf of Mexico with faster and more accurate tsunami warnings. The tsunameters employ the patented technology of the second generation Deep-ocean Assessment and Reporting of Tsunamis (DART® Π). A full year of operating the completed network provided a host of challenges and accomplishments. Data availability statistics missed the operating goal of 80%, primarily due to a rash of mooring failures. Most of these failures occurred in regions of strong ocean currents — the Kuroshio Current, the Loop Current of the Gulf of Mexico, and the Gulf Stream. Stations in the western North Pacific Ocean experienced prolonged outages because of the great distances from staging areas and persistent stormy weather and their proximity to major storm tracks. However, in 2007 the mooring and system at station 42407, in the Caribbean, had exceeded design specifications by weathering the passage of Hurricane Dean, when it was a Category 4 hurricane. In the spring and summer of 2009, a series of ambitious service cruises will return the network to nearly full operating capability. Focusing on ways to reduce future outages, NDBC undertook a number of engineering initiatives, including an intensive investigation into the mooring failures and deployed several new mooring types for evaluation and obtained warehouse space in Guam to reduce logistical requirements. In response to requirements from the US Tsunami Warning Centers (TWC) — the Pacific Tsunami Warning Center, Ewa Beach, Hawai'i and the West Coast/Alaska Tsunami Warning Center, Palmer, Alaska — the 2009 deployments included new firmware that provided the TWCs more control and improved initiating event or rapid reporting mode. Previous firmware versions added an artificial 100 mm to the estimated water-column height in order to initiate and indicate rapid reporting mode by command from the TWCs. Command-initiated modes are now distinguished from on-board-initiated modes by new message identifiers. NDBC made changes to the electronics to reduce the number of false event modes that have made up about a third of all event mode initiations. The changes will also prevent the corruption of transmitted data caused by feedback during the acoustic transmissions. In 2009, NDBC completed the initial field test and evaluation of its new Standard Buoy, configured for tsunameter operations and its first operational use at Station 46412. The Standard Buoy will provide a common, lower-cost platform that can be used interchangeably with NDBC's other buoy programs — Weather and Oceanographic Platforms (WxOP) and the Tropical Atmosphere Ocean (TAO) Array Buoys. In addition, Standard Buoys will have the capability to provide multi-purpose capabilities, such as making meteorological measurements at tsunameter stations. During the past year, NOAA added the tsunameter messages to its NOAAPORT broadcast system that provides NOAA's environmental data and information to external users through a commercial provider.