SPATIAL-SCALE ANALYSIS OF HYDROGRAPHIC DATA OVER THE TEXAS-LOUISIANA CONTINENTAL-SHELF

Citation
Yx. Li et al., SPATIAL-SCALE ANALYSIS OF HYDROGRAPHIC DATA OVER THE TEXAS-LOUISIANA CONTINENTAL-SHELF, J GEO RES-O, 101(C9), 1996, pp. 20595-20605
Citations number
19
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Oceanografhy
Journal title
JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS
ISSN journal
2169-9275 → ACNP
Volume
101
Issue
C9
Year of publication
1996
Pages
20595 - 20605
Database
ISI
SICI code
2169-9275(1996)101:C9<20595:SAOHDO>2.0.ZU;2-O
Abstract
On the basis of hydrographic data collected by the Texas-Louisiana She lf Circulation and Transport Processes Study (LATEX A) and on earlier cruises, we examined the energetic scales of spatial variability over the Texas-Louisiana continental shelf. Shelf-scale spatial reference f ields were sought to represent the general distributions of circulatio n and water properties over the shelf at the time of the observations. Various methods were explored for determining such reference fields o f potential temperature, salinity, and geopotential anomaly at the sea surface relative to 70 dB. Spatial reference fields obtained from mea n May fields and from polynomials fitted to individual May cruise data were compared. On the basis of those comparisons, quadratics were sel ected to fit property distributions from individual cruises and so to yield reference fields. Smaller-scale anomaly fields were obtained by removing the reference fields from the observed distributions. Calcula tion of correlation versus separation distance based on these anomaly fields then allowed estimation of spatial scales of anomaly fields for cross-shelf and along-shelf transects. The zero-crossing scale and th e Gaussian decay scale are shown to be essentially the same, and the z ero-crossing scale is used. The principal results for the anomaly scal es are (1) cross-shelf scales over the western shelf are shorter (orde r 15 km) than those in the eastern and central regions (order 20 km), (2) along-shelf spatial scales are of the order of 35 km, (3) there is no significant difference in cross-shelf scales at the surface, midde pth, and bottom, and (4) along-shelf scales are essentially the same o ver the western and eastern regions of the shelf, over the midshelf (5 0-m isobath) and along the shelf break (200-m isobath), and at differe nt depths along the 200-m isobath. The same spatial scales are found w hen using data with spatial resolution of 1-10 km cross shelf and 10-2 0 along shelf to obtain the anomaly fields, so the data resolution use d is adequate to represent the scales. The variances of the observed ( shelf-wide) salinity, temperature, and geopotential anomaly are greate r cross shelf than along shelf. The variance of the cross-shelf anomal y fields is around 10% of the shelf-wide fields; that of the along-she lf anomaly fields is about 35% of that in the shelf-wide fields, The a nalysis of scales when grouped by season did not show persuasive evide nce of seasonal variation.