Importance of grid-cell area in the estimation of estuarine residual fluxes
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Estuaries Vol. 21, No.1, p. 14-28 March 1998 Importance of Grid-Cell Area in the Estimation of Estuarine Residual Fluxes 1 GERARDO M. E. PERILL0 2 Instituto Argentino de Oceanografta CC 107 8000 Bahia Blanca Argentina and Departamento de Geologia Universidad Nacional del Sur Sanjuan 670 8000 Bahia Blanca Argentina M. CINTIA PICCOLO Instituto Argentino de Oceanografta CC 107 8000 Bahia Blanca Argentina and Departamento de Geografia Universidad Nacional del Sur 12 de Octubre y San Juan 8000 Bahia Blanca Argentina ABSTRACf: Estimation of residual fluxes in estuarine cross sections is a very important procedure to establish, among others aspects, residence time of contaminants, circulation pattern, and sediment transport dynamics. However, the analytical procedure to obtain such values is not trivial and is presented in detail, demonstrating the importance of the grid-cell area as a weighting element in the calculation of spatial averages. The procedure is tested with four different grid designs and it is shown that grids with proportional columns and rows are the only ones that do not introduce statistical noise in the estimation of the residual fluxes. The four designs are also tested with data from a cross section of the Bahia Blanca Estuary (Argentina), results again show that the proportional columns and rows grid provide the best approach in calculating residual fluxes. Introduction Since Bowden (1963) proposed that any instan- taneous measurement obtained in an estuary could be decomposed into several contributions, the study of residual fluxes over one or several cross sections in estuaries has become a major issue in estimating the different residual circulations and dispersion coefficients. Studies made by Fisher (1972), Dyer (1974), Murray and Siripong (1978), Iqerfve and Proehl (1979), Uncles and Jordan I Instituto Argentino de Oceanografia contribution number 400. 2 Corresponding author; tele (54-91) 86-1112/1519; fax (54- 91) 86-1527; e-mail [email protected]. © 1998 Estuarine Research Federation 14 (1980), Uncles et al. (1985, 1986), and Iqerfve et al. (1981, 1982) were pioneer research, providing the basis for many interpretations of several types of fluxes that arise from the different interactions. The flux of salt transported through a cross sec- tion per unit time (F) is represented by F = fA USdA (1) where U is the longitudinal component of the ve- locity, S is the salinity, and A is the area of the cross section. Equation (1) can be extended to any con- servative parameter that may be measured simul- taneously with the water velocity. Murray and Siri- pong (1978) developed an analytical method to calculate the transport of mass and salt through a
Transcript of Importance of grid-cell area in the estimation of estuarine residual fluxes
Estuaries Vol. 21, No.1, p. 14-28 March 1998
Importance of Grid-Cell Area in the Estimation of Estuarine Residual
Fluxes1
GERARDO M. E. PERILL02
Instituto Argentino de OceanograftaCC 1078000 Bahia BlancaArgentinaandDepartamento de GeologiaUniversidad Nacional del SurSanjuan 6708000 Bahia BlancaArgentina
M. CINTIA PICCOLO
Instituto Argentino de OceanograftaCC 1078000 Bahia BlancaArgentinaandDepartamento de GeografiaUniversidad Nacional del Sur12 de Octubrey San Juan8000 Bahia BlancaArgentina
ABSTRACf: Estimation of residual fluxes in estuarine cross sections is a very important procedure to establish, amongothers aspects, residence time of contaminants, circulation pattern, and sediment transport dynamics. However, theanalytical procedure to obtain such values is not trivial and is presented in detail, demonstrating the importance of thegrid-cell area as a weighting element in the calculation of spatial averages. The procedure is tested with four differentgrid designs and it is shown that grids with proportional columns and rows are the only ones that do not introducestatistical noise in the estimation of the residual fluxes. The four designs are also tested with data from a cross sectionof the Bahia Blanca Estuary (Argentina), results again show that the proportional columns and rows grid provide thebest approach in calculating residual fluxes.
Introduction
Since Bowden (1963) proposed that any instantaneous measurement obtained in an estuarycould be decomposed into several contributions,the study of residual fluxes over one or severalcross sections in estuaries has become a major issuein estimating the different residual circulationsand dispersion coefficients. Studies made by Fisher(1972), Dyer (1974), Murray and Siripong (1978),Iqerfve and Proehl (1979), Uncles and Jordan
I Instituto Argentino de Oceanografia contribution number400.
2 Corresponding author; tele (54-91) 86-1112/1519; fax (5491) 86-1527; e-mail [email protected].
© 1998 Estuarine Research Federation 14
(1980), Uncles et al. (1985, 1986), and Iqerfve etal. (1981, 1982) were pioneer research, providingthe basis for many interpretations of several typesof fluxes that arise from the different interactions.
The flux of salt transported through a cross section per unit time (F) is represented by
F = fA USdA (1)
where U is the longitudinal component of the velocity, S is the salinity, and A is the area of the crosssection. Equation (1) can be extended to any conservative parameter that may be measured simultaneously with the water velocity. Murray and Siripong (1978) developed an analytical method tocalculate the transport of mass and salt through a
