© Copyright Institute of Electrical and Electronics Engineers 1995
flament_igarss1995a.html
SIR-C/X-SAR observations of convergent
fronts in the Central Equatorial Pacific
Flament,
P. Holt, B.
Dept. of Oceanogr., Hawaii Univ.,
Honolulu, HI , USA;
This paper appears in: Geoscience
and Remote Sensing Symposium, 1995. IGARSS '95. 'Quantitative Remote
Sensing
for Science and Applications', International
Meeting Date: 07/10/1995 - 07/14/1995
Publication Date: 10-14 July 1995
Location: Firenze
Pages: 1323 - 1324
Volume: 2
Abstract:
The
surface front separating cold equatorial water from warmer tropical
water
at 2-7°N in the Central Pacific was studied twice for one week in
April and
October 1994 between 115°W and 155°W with the SIR-C/X-SAR
synthetic aperture
radar, with supporting NOAA satellites infrared images. During the
October
flight (the peak of the equatorial upwelling season), zonal linear
features
of enhanced backscatter intensity were observed at all wavelengths, and
corresponded
closely to the thermal front seen in the infrared images. A striking
example
of such feature is seen in an X-band real time image. On some data
takes,
several linear features were found at different latitudes, suggesting
that
the front may not have been unique. The motion of the front estimated
from
successive daily images was consistent with the westward propagation
found
by previous studies. In contrast, no fronts were observed in the images
taken
during the April flight, which were dominated by the surface signature
of
rain cells. The front was also visible as brightness changes in AVHRR
images
of the Sun glint, and photographs of the glint taken from the Space
Shuttle
show the equatorial front as a quasi-linear feature, often darker than
surrounding
water. These observations are consistent with in situ data collected
during
the Tropical Instability Wave Experiment in 1992 and 1995.
Fine-structure
was observed, suggesting northward subduction of cold, high salinity
equatorial
water, beneath warmer less saline ITCZ water. A 40 km drifter array
deployed
on the cold side of the front became aligned with the front in less
than
3 days. The velocity averaged over five frontal crossing showed a 10
km-wide
westward jet of 90 cm/s and a cross-frontal convergence of 15 cm/s,
both
confined above the thermocline. During these cruises, whitecapping was
frequently
enhanced over a band ~100 m wide near the front
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