Abstract
In order to examine characteristics of secondary undulation in Urauchi Bay of Kamikoshiki Island, direct measurements of sea level, current velocity and atomospheric pressure were made during February 10 - March 31 in 2012. It was found from the observational results that the first-mode oscillation with the 23.8-minute period and the second-mode oscillation with the 12.5-minute period were dominant in the bay. Moreover, it was clarified that the ratio of the amplitude of the first-mode oscillation at the mouth of the bay to that at the Oshima fishing port is 1:8.7 on average, while the ratio of the amplitude of second-mode oscillation at the mouth of the bay to that at the Oshima fishing port is 1 : 8.9 on average. The occurrence of the large secondary undulation in Urauchi Bay depends mainly on the the second-mode oscillation with the 12.5-minute period.
