Katsuyoshi Shimizu

BASIC DESIGN OF JAPANESE NATIONWIDE GPS BUOY NETWORK WITH MULTI-PURPOSE OFFSHORE OBSERVATION SYSTEM

This paper introduces a basic design of GPS buoy multi-purpose data processing system using numerical filtering analysis. GPS buoy system and future plan of the GPS buoy network in Japan are introduced. Tsunami detection system with time series is considered. Directional wave analysis and offshore wind and current analysis methods are also investigated.

Offshore Winds and Currents Observation by GPS Buoy with Numerical Filtering Analysis

This paper introduces basic design of the GPS buoy multi-purpose data processing system for offshore information. The system consists of real-time tsunami detection, directional wave analysis, infragravity wave analysis, offshore wind observation, and current observation. For real-time tsunami detection, applicability of the GPS buoy system using the proposed numerical filtering techniques was confirmed with the prototype observation during 2004 Tokaido-off Earthquake Tsunami event. The GPS buoy system is able to distribute directional wave information within the corresponding wave periods of between 6 and 30 seconds, using the frequency banded spectrum analysis method. Offshore winds data were compared with that of on-land station at 225 m high on the Muroto-Misaki. It was found that buoy motion correction is necessary only when we need instantaneous maximum wind speed. GPS buoy is also able to observe offshore currents by the frequency banded analysis.

Characteristics of the Observed Offshore Wave Data by the GPS Buoys

This paper explained characteristics of the observed offshore wave, tsunami and tide data for the half year in 2007, obtained by the two sets of the GPS buoy system installed off the Northern Pacific Coast of Japan by the Ports and Airports Department of the Tohoku Regional Development Bureau of the Ministry of Land, Infrastructure and Transport Japan. Two sets of the GPS buoy successfully observed, wave climate, abnormal high waves, and offshore astronomical tides with little data luck only about 2% of the total observation data. Offshore GPS buoys observed much bigger significant wave heights in both normal and abnormal sea states than the shallower seabed wave gauges, meaning that deep-sea wave observation is necessary in order to obtain offshore wave conditions.

DEVELOPMENT OF THE OFFSHORE WIND AND POWER-GENERATION RATE ESTIMATION SYSTEM BASED ON FIELD DATA

A new system was developed to estimate wind velocity distribution around the offshore wind-power generators, by assuming the wind energy conservation equation. Based on the long-term wind and power-generation observed data at the offshore and on-land stations, applicability of the tri-dimensional numerical wind simulation based on the k-e model was confirmed. Interactions among the wind-power generators were estimated by using the numerical simulation, and example of the estimated power generation rate distribution around the existing generators was introduced. It was concluded that wind power generators reduce the wind velocity and wind-power potential of the surrounding sea-surface in the large area more than 5 times of the wind generators diameter.