The Port and Airport Research Institute engaged in the routine statistical analysis on waveforms acquired through the Nationwide Ocean Wave Information Network for Ports and Harbours (NOWPHAS) from 1970. The network has wave gauges on 20–50 m deep seabed and GPS-mounted buoys at 100–400 m deep sites over Japan. This paper summarizes the half-century-long history of the network, the data processing procedure, and major statistics by referring recent ISOPE conference papers and conducting additional wave data analysis.
Fig. 1 shows that the four ocean/seas surround the Japanese islands. Summer and autumn typhoons bring high waves on the Pacific coast, and winter pressure patterns, which have high and low pressure systems to the west and east of Japan, respectively, and moving extratropical cyclones affect the Sea of Japan, the East China Sea, and the Okhotsk Sea coast. Sea ice covers a part of the Okhotsk Sea in winter. Wave observation was only one reliable way to investigate sea conditions a half century ago and plays an indispensable role together with numerical wave models to understand deeply in recent years when ocean development and future climate change are great interests.
On this background, the Japanese port organizations have been conducting the nationwide wave information network since 1970. Among these organizations, the Port and Harbour Research Institute (PHRI) and its successor, the Port and Airport Research Institute (PARI), engaged in core technical works such as the final analysis on wave data, the issue of annual reports, and the development of equipment and analysis methods. But these were generally publicized in Japanese only.
This paper is a great chance to summaries the half-century-long history of the network, the present data processing procedure, and major statistics, in English, by referring recent ISOPE conference papers and conducting additional wave data analysis.
The Japanese port organization team chose 14 sites over Japan for wave observation in 1968 and then began the operation at 10 sites in 1970. The team consists of the Ports and Harbours Bureau as the headquarter, the First to Fifth District Port Construction Bureaus, and PHRI, of the Ministry of Transport; and the Hokkaido Development Bureau, of the Hokkaido Development Agency. Fig. 1 shows the layout of these 10 sites as P01–P10. These measurements were water pressure gauges (PW), ultrasonic wave transmitters/receivers (USW), and step-type recording wave gauges (SRW) on less than 20m deep seabed (Takahashi et al, 1972). Magnetic tapes and paper sheets were recorded at the port construction offices and then were sent to PHRI by post mail. The observation aimed to obtain the design criteria for port structures and the calmness statistics for construction works.