JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 106, NO. C12, PAGES 31, 057–31, 073,
2001
Surface current variability east of Okinawa Island obtained from remotely sensed and in situ observational data
Yukiharu Hisaki
Department of Physics and Earth Sciences, Faculty of Science, University of the Ryukyus, Okinawa, Japan
Tsutomu Tokeshi
Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Fukuoka, Japan
Wataru Fujiie
Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Fukuoka, Japan
Kenji Sato
Okinawa Radio Observatory, Communications Research Laboratory, Okinawa, Japan
Satoshi Fujii
Okinawa Radio Observatory, Communications Research Laboratory, Okinawa, Japan
Abstract
We investigated ocean surface current variability
in the region east of Okinawa Island in the spring of 1998 using in situ
and remotely sensed data including surface velocity
estimates inferred from HF ocean radars. Most previous studies
utilizing
HF ocean radars were limited to shallow continental
shelves. In contrast, most of the observation area in this study was in
the open ocean. During the observation period the
HF ocean radars sampled a region where anticyclonic and cyclonic
mesoscale
eddies were adjacent to each other. The
HF-radar-derived ocean currents agree with those measured by a current
meter. The
surface currents were highly variable in both time
and space and were affected by the eddy field in the offshore region.
The
current field was related to the near-surface water
temperature. For example, a local temperature rise was often associated
with northeastward flows. The surface currents in
regions shallower than about 1000 m had a significant correlation with
local
wind forcing. Our HF ocean radars often detected a
strongly convergent zone, which was different in character from those
described
in previous studies in that it was in the deep
ocean. From other data such as National Oceanic and Atmospheric
Administration
advanced very high resolution radiometer imagery,
we concluded that the convergent zone was due to mesoscale eddy fronts.
Received 2
January
2001;
accepted 10
July
2001.
Citation: Hisaki, Y., T. Tokeshi, W. Fujiie, K. Sato, and S. Fujii (2001), Surface current variability east of Okinawa Island obtained from remotely sensed and in situ observational data, J. Geophys. Res., 106(C12), 31, 057–31, 073.
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