Nationwide Ocean Wave Information Network For Ports And HArbourS Research Articles

Developments of GNSS buoy for a synthetic geohazard monitoring system.

A global navigation satellite system (GNSS) buoy system for early tsunami warnings has been developed for more than 20 years. The first GNSS buoy system using a real-time kinematic algorithm (RTK) was implemented in the Nationwide Ocean Wave information network for Ports and HArbourS (NOWPHAS) wave monitoring system in Japan in 2008. The records of NOWPHAS were used to update the tsunami alert by the Japan Meteorological Agency (JMA), owing to the tsunami generated by the 2011 Tohoku-oki earthquake (Mw9.0). However, considering that the distance limit is less than 20 km for the RTK algorithm, a new system was designed by introducing a new positioning algorithm and satellite data transmission to place the buoy much farther from the coast. A new technique for the continuous monitoring of ocean-bottom crustal movements was also implemented in the new system. The new buoy system can be used for weather forecasting and ionospheric monitoring as well.

Empirical relationship of tsunami height between offshore and coastal stations

This study compares tsunami height data obtained by coastal tidal stations and offshore wave stations of the Nationwide Ocean Wave information network for Ports and HArbourS (NOWPHAS) with data obtained from real-time kinematic global positioning system (RTK-GPS) buoys. NOWPHAS wave stations and RTK-GPS buoys are typically installed off the coast—the former within several kilometers of the coast and the latter 2–20 km offshore. The ratio of initial tsunami height observed at a coastal tidal station to that observed at an offshore station was found to be approximately proportional to the fourth root of the ratio of the sea-bottom depths to the mean sea level at the respective offshore and coastal station. This approximation can also be applied to maximum tsunami amplitudes. The relationship derived in this paper will enable the initial tsunami height to be forecast by real-time applications using detected tsunami initial height from offshore stations, such as the sea-bottom pressure gauges of NOWPHAS stations and RTK-GPS buoys.

Real-time Wave Prediction using Hourly Analyzed Atmospheric GPV and Its Verification

This study developed a real-time wave prediction system by using SWAN (Simulating WAves Nearshore) with the data of hourly analyzed atmospheric GPV (Grid Point Value). The validity of this system was carried out by comparing the predictions with observations from NOWPHAS (Nationwide Ocean Wave information network for Ports and HArbourS) during one month of December, 2007. The predicted wave heights and periods well corresponded to the observed ones. By using this system, wave situations at present and short-term future can be estimated for locations where there are no wave observation equipments.

Characteristic of the Observed Abnormal Waves Caused by the 2006 Typhoons and Low-Pressures

This paper introduces the abnormal sea states observation records caused by the Typhoons No.0612, 0613 and low-pressures combined with the Typhoon No.0616 and 0617. Observed wave data were obtained from Japanese Nationwide Ocean Wave in formation network for Ports and HarbourS (NOWPHAS) network. Ten of the NOWPHAS 60 wave stations recorded historical maximum observed significant waves during the 3 major events. Both zero-up-cross wave-to-wave analysis and spectrum analysis were conducted to explain those abnormal wave characteristics. Low frequencys wellsw ith significanwt ave periodsl onger than 15 secondsw ere observeda longt he northern Pacificc oasts with several days duration during the Typhoon No.12 attack.

Characteristic of the Observed Tsunami Profiles of the 2006 and 2007 Chishima-Islands-off Earthquakes

The 2006 Chishima-Islands-off Earthquake was generated around 20: 14 on November 15 in 2006 in Japanese standard time (JST). It was reported by the Japan Meteorological Agency (JMA) that the magnitude of the earthquake was 7.9, and the hypocenter was at off-Chishima-Islands Pacific side coast, with the latitude of N46.7°, the longitude of E154° and 30km deep under the seabed. Two months after the earthquake, 2007 Chishima-Islands-off Earthquake was generated around 13: 23 on January 13 in 2007 (JST) with the magnitude of the earthquake 8.2 and the hypocenter of the latitude of N46.3°, the longitude of E154° and 10km deep. This paper introduces the observed tsunami profiles by the Nationwide Ocean Wave information network for Ports and Harbour S (NOWPHAS).

ブイの動揺を考慮したＧＰＳ波浪計による洋上風観測

Newly developed GPS buoy system, applying the RTK-GPS techniques to measure the exact movement of the offshore floating buoy, is supposed to be the future principal offshore wave and tsunami observation equipment for Japanese NOWPHAS (Nationwide Ocean Wave information network for Ports and HArbourS). By installing a wind gauge at the top of the buoy, offshore wind information is also applicable, which is important for various offshore economical activities such as fishery, clean energy development etc., with proper correction of the observed data with consideration of the buoy motion effects. This paper introduces results of study on buoy motion correcting methods by using proto-type data obtained off-Muroto-Misaki.

外洋性港湾における出入港時諸問題の現地調査 : 日本海に面した港湾での波浪特牲の分析

In this study, it is necessary to find out some problems about the ship operation in harbours facing to open seas. At first, the hearing research is carried out for many harbours nationwide to know present operational situations and problems. Then, we research on the operation record of the maritime company in the harbour (H Port) facing to the Sea of Japan. Moreover, wave data are analyzed for one of the observation points of NOWPHAS (Nationwide Ocean Wave information network for Ports and HArbourS) near the harbour when ship operations become impossible in recent years. Some relations can be found between operational records and waves. Therefore, main conclusions are obtained as follows. (1) Operators feel so difficulties for ships on the safety of departing and entering harbours facing to open seas when sea conditions are serious. (2) It is cleared that waves are the most important factor to evaluate the safety of ship-handling in harbours facing to open seas. (3) The most dangerous situation is occurred for entering ships when they are altering course near harbours in following seas. (4) The operation becomes impossible in H Port when significant waves become more than 2.0m and 6s in winter season. (5) When the ship operation becomes difficult in H Port, wave heights grow about wave components in 5-8s at first. Then, wave heights tend to grow about wave components in 8-12s with 2-8hours of time lag in most cases. However, these wave heights grow at the same time in some cases. It is necessary to research on growth patterns of waves in detail when ships cannot operate in the future.

Frequency Banded Wave Climate Description Based on the Observed Directional Spectra

A new system for directional wave spectrum observation was developed by improving the Nationwide Ocean Wave information network for Ports and HArbourS (NOWPHAS). Either Doppler Type Wave Directional Meter (DWDM) or Wave Gauge Array System is adopted for wave observations. Directional spectra are estimated by EMLM method for DWDM and EMEP method for array system. For the convenience, the obtained directional spectra are expressed as the frequency banded wave heights and directions corresponding to the wave spectrum. Examples of annual statistics of the directional wave spectra at three typical NOWPHAS wave stations are introduced in this paper.

NATIONWIDE COASTAL INFRA-GRAVITY WAVE OBSERVATION NETWORK BASED ON CONTINUOUS DATA SAMPLING AND FREQUENCY BANDED SPECTRUM EXPRESSION

This paper introduces Japanese Nationwide Ocean Wave information network for Ports and HArbourS (NOWPHAS) system, which recently improved for the directional and infra-gravity wave observation with continuous data aquisition. New concept of frequency banded expression has been introduced in the data analysis of directional and infra-gravity waves. Examples are demonstrated as the time series and annual statistics forms observed by the Japanese NOWPHAS system.The NOWPHAS new wave data acquisition and analysis system clarified the characteristics of the long period swells originated from typhoons and low pressures, and the 2001 Peru Earthquake Tsunami.

POTENTIAL OF WIND POWER AROUND JAPANESE COASTAL AREAS UTILIZING NOWPHAS SYSTEM DATA

Wind energy for electric power generation was estimated around all over the Japanese coastal area. Observed wind data every 2 hours for four years at twenty-nine stations were acquired by using the Nationwide Ocean Wave information network for Ports and HarbourS (NOWPHAS) system. Results of the observed wind statistical analysis showed that wind characteristics on seas are much more suitable for the power plants than ones on lands.