ADCP OBSERVATION OF NEARSHORE CURRENT STRUCTURE IN THE SURF ZONE

Takao Yamashita, Hiroshi Yashioka, Shigeru Kato, Lu Ming, Chikara Shimoda

Abstract


Coastal current in the nearshore zone is generated by both breaking waves inside the surf zone and by the wind over the extended area of the coastal and offshore zones. Wind-induced currents as well as wave-induced currents are characterized by strong shearflows and complicated turbulence flow fields. In order to develop mathematical models for these currents, it is essential to formulate wind and wave stresses acting on the sea surface. Unfortunately, there has been no reliable observation of current profile in the surfzone under the condition ofstrong wind. No extensive information on wind stresses inside the nearshore zone has been made available, primarily because of the challenge ofrecording these data without facilities such as observation pier or towers. In this paper we conducted a continuous recording ofnearshore current profile and wind stresses in/out the surf zone by using high frequency ADCP (Acoustic Doppler Current Profiler, 1200kHz) installed on the sea bottom under the observation pier of Ogata Wave Observatory, together with 3-component ultrasonic anemometer. This two and halfmonths observation revealedpart of the structure of nearshore currents and some characteristics of the wind drag coefficient in the nearshore zone.

Keywords


surf zone; current; nearshore current; ADCP observation

Full Text: PDF

Creative Commons License
This work is licensed under a Creative Commons Attribution 3.0 License.