2007 Annual Report - jamstec japan agency for marine-earth ...

in the equatorial Indian Ocean
Since ocean currents data observed with ADCP moorings
deployed on the equator in the eastern Indian Ocean by
National Institute of Oceanography, India and by Pacific
Marine Environment Laboratory/National Oceanic and
Atmospheric Administration, U.S.A. are available through
international cooperation, we can acquire zonal structure of current
profile on the equator from 80E to 90E, corresponding to
off the coast of south of India to that of Sumatra. Using these
data we conducted comprehensive statistical analysis for upper
ocean currents. Basically the mean currents indicate vertically
2-layer structure; one velocity core appears around 60 m and
the other appears around 120 m, corresponding to the equatorial
undercurrent. 30-50 days signal in the uppermost layer and
semiannual signal in the region of equatorial undercurrent are
dominant for the zonal current, whereas about 14 days signal
corresponding to the mixed Rossby-gravity wave is dominant
for the meridional current. We also investigated wave-propagating
character from phase relationship between current property
off the coast of south of India and that of the coast of Sumatra.
The 35-day signal, which is predominant in the uppermost
layer, propagates eastward with a phase velocity of 6.4 m s -1 .
We suggest that this signal is caused by atmospheric disturbances.
The semiannual signal, which is predominant in the
region of the equatorial undercurrent, propagates eastward with
a phase velocity of 2.4 m s -1 , corresponding to the Kelvin wave
of first baroclinic mode.
d. Development of the new observation system
In the development of a high accuracy TRITON buoy, the
measurement of sea surface temperature was conducted by
using the TRITON buoy at Equator 156E under the cooperation
with the Tohoku University. With the parallel operation of
a large number of the next generation buoys and a small number
of the high accuracy reference buoys, the development of
the surface buoy network in the tropical region has progressed
one step forward for the efficient operation of the buoys and to
satisfy the needs of more advanced research.
Argo Group
As one of the leading groups in the international Argo
community, Argo Group is responsible for the deployment of
Argo floats mainly in the north Pacific and for the operation of
the PARC (Pacific Argo Regional Center). Argo float data is
released both in real-time and in delayed mode. After receiving
data from the Argos satellites, Japan Meteorological Agency
releases it as real-time data to the worldwide meteorological
organizations via GTS (Global Telecommunication Systems)
within 24 hours, and Argo Group carries out high level quality
controls to the Argo float data and sends it as delayed-mode
data to GDAC (Global Data Assembly Center) within a year.
Both real-time and delayed-mode data are available to anyone
in the world by accessing to GDAC via internet with no charge.
Using Argo float data, Argo Group conducts observational
researches on several themes in the north Pacific such as seasonal
to inter-annual variations, the subduction process, the formation
and transport processes of several types of mode waters,
temperature and salinity variations in the subtropical and tropical
regions, and the oceanic structure in the subarctic region.
Argo Group is also developing a next-generation float.
a. Deployment of Argo floats
According to the deployment plan of FY2007, Argo Group
deployed 80 floats in the Pacific, Indian, and Southern Oceans.
Fig. 5 (a)Time-depth section of the ocean temperature observed by the
TRITON buoy at 5S, 95E. Colors (contours) denote anomalies (raw values).
Contour interval is 2C. The black line indicates the mixed layer
depth. (b)Terms of the mixed layer temperature balance. The black line
indicates temporal change of mixed layer temperature, the red line indicates
contribution of net sea surface heat fluxes, and the blue line indicates
contribution of the horizontal heat advection.The unit is C/day.
Terms of the mixed layer temperature balance (1) [C/day]: (a) temporal
change (T/t, black) and net heat fluxes (Q net /_C p H, red); (b) T/t (black)
and zonal (- UT x , red) and meridional (- VT y , blue) horizontal heat advection
and their sum (-UT x -UT y , green); and (c) T/t (black) and the sum
of Q net /_C p H and - UT x - VT y (gray). Also shown in (d) is the time-depth
section of temporal change in ocean temperature and the MLD. In (a)-
(c), light shading indicates the errors in the analysis. Details of the error
estimation are presented in the Appendix.
At present, 348 Argo floats owned by JAMSTEC are working
well. By the great international cooperation, the global Argo
float network attained the initial target of 3,000 floats at the end
of October 2007 and maintains the same level in March 2008
(Fig.1-6).
b. Delayed-mode quality control of Argo float data and operation
of PARC
Argo Group released about 12,000 profiles as real-time
data and about 16,000 profiles as delayed-mode data. PARC,
which started in 2005, plays an important role to maintain the
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