New Zealand Journal of Marine and Freshwater Research abstracts
Determining the internal structure of the ocean off north-east New Zealand from
surface measurements
STEPHEN M. CHISWELL
National Institute for Water & Atmospheric
Research Ltd
P. O. Box 14 901
Wellington, New Zealand
email: s.chiswell@niwa.cri.nz
Abstract The assumption that variability in the circulation
around the east coast of the North Island of New Zealand can be described using
satellite-derived sea level and temperature and two empirical modes is tested.
Potential errors are quantified if such an assumption is used to derive the
internal fields from surface observations. Data from 303 CTD
(conductivity-temperature-depth) casts made in the region between 1994 and 1999
are first tested against a much larger XBT (expendable bathythermograph) data
set to show that they are representative of the expected variability, and then
used to compute the empirical modes. The empirical modes are not baroclinic
modes, but probably represent the lateral meanderings and variations in
strength of the East Auckland Current, together with the presence of Rossby
waves in this region. If surface temperature and height can be measured
precisely, 60-70% of the variance in the internal temperature and velocity
perturbations can be explained with the model. The standard deviation of
reconstructed internal temperature errors is about 0.6deg. near the surface and
less with depth. The standard deviation in velocity errors is 5 cm
s
-1.
Keywords East Auckland Current; vertical structure
M00026
Received 6 June 2000; accepted 5 October 2000
New Zealand Journal of Marine and Freshwater Research, 2001, Vol. 35:
289-306
0028-8330/01/3502-0289 $7.00 (c) The Royal Society of New Zealand
2001
PDF file of entire paper: medium quality (2468K); (scanned from paper original: notes about this process)
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