GULF-STREAM SURFACE CONVERGENCE IMAGED BY SYNTHETIC-APERTURE RADAR

Citation
Go. Marmorino et al., GULF-STREAM SURFACE CONVERGENCE IMAGED BY SYNTHETIC-APERTURE RADAR, J GEO RES-O, 99(C9), 1994, pp. 18315-18328
Citations number
37
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Oceanografhy
Journal title
JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS
ISSN journal
2169-9275 → ACNP
Volume
99
Issue
C9
Year of publication
1994
Pages
18315 - 18328
Database
ISI
SICI code
2169-9275(1994)99:C9<18315:GSCIBS>2.0.ZU;2-1
Abstract
On July 20, 1990, the north edge of the Gulf Stream (36.7-degrees-N, 7 2.0-degrees-W) was sampled by the R/V Cape Henlopen and simultaneously imaged by the Jet Propulsion Laboratory's airborne synthetic aperture radar (SAR). Hydrographic measurements show an abrupt surface front s eparating warm, salty Gulf Stream water in the south from a filament o f cool, fresh (<33 practical salinity unit (psu)) water to the north. The filament lies within the stream and is likely water entrained from the continental shelf. The southern boundary of the filament is marke d by increased surface wave breaking in a 100- to 200-m-wide zone, acc umulations of Sargassum, and an orthogonal velocity change of 20 cm/s. The front is manifested in a sequence of SAR images as a narrow line having returns 1-2 dB higher than background. (A second, transient SAR line occurs near the northern filament boundary.) The observations ar e compared with model calculations of the surface wave hydrodynamics a nd radar scattering. The ocean waves are driven by southwesterly 8-m/s winds and interact with the front to produce primarily an enhancement of 2- to 3-m waves over a less-than-or-equal-to200-m-wide region cent ered downwind of the front. Using a composite scattering radar model a long with measured breaking-wave statistics, we show that the observed modulations in the radar backscatter can be accounted for through bre aking-wave and tilted Bragg wave scattering effects. These results fur ther show that SAR images of the ocean surface can be exploited for de tailed study of particular ocean processes.