平塚沖波浪観測資料(7)(1986.9〜1988.8)

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Wind wave observation at the Hiratsuka Marine Observation Tower has been conducted continuously since 1978, and data reports and summary results have been published in six back issues of 'Review of Research For Disaster Prevention' (Nos.38, 47, 59, 107, 123 and 135). This issue contains those data for the period from September 1986 to August 1988. Descriptions of the tower are presented in Figs.1 and 2. An ultrasonic wave gauge has been used for wave measurements since December 19, 1986, while an electric capacitance type one worked until December 18, 1986. The characteristics of the ultrasonic sensor is almost same as those of the capacitance type as shown in Fig4, except for the highest frequency range where statistic contribution to the significant wave is very small (Fig.5). Wind speed and direction are measured by an Aero-vane type anemometer on a mast at the top of tower where the height above the mean sea level is 22.5 m. Atmospheric pressure presented here was measured at the base laboratory located on shore before November 29, 1987, and have been measured in the hut of the tower after November 30, 1987. Wave, wind and atmospheric pressure data measured on the tower are transmitted to the base laboratory through a submarine cable, and acquired in real time by a telemeter system (Fig.6) at a rate of one sample every 0.3 seconds for each channel. The one-over-three significant wave heights (H_<1/3>) and periods (T_<1/3>) are calculated from 20 minutes wave data centered at every exact hour. Analysed results are presented as follows : (1) Events of rough sea condition that occured during the period are described in Table 1. (2) Monthly traces of the significant waves, atmospheric pressures and winds are shown in Fig.7. A mean wind direction and speed averaged over 10 minutes centered at the first exact hour of every three hours are indicated by a vector. (3) Wave height is plotted in Fig.8 against significant wave period observed during each month. (4) Monthly wind-roses are shown in Fig.9. The upper figure shows the number of the monthly frequency distribution of observed wind directions in each direction and the lower shows the monthly mean wind speed observed in each direction. (5) Table 2 shows the number of times of a given wave-height observed with each wave period of significant waves. Each dot in Fig.8 is classified and counted for every 30 cm of wave height and for every 1.0 second of wave period.
独立行政法人防災科学技術研究所の論文
1990-03-30

平塚沖波浪観測資料(7)(1986.9〜1988.8)

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