HR: 1330h
AN: OS23A-04    [Abstracts]
TI: Evaluation of Bio-optical Algorithms for Chlorophyll Mapping in the Southwestern Atlantic
AU: Garcia, V M
EM: docvmtg@furg.br
AF: Federal University of Rio Grande (FURG), Dept. of Oceanography, Av. Italia, Km 8, Rio Grande, RS 96201-900 Brazil
AU: * Garcia, C A
EM: dfsgar@furg.br
AF: Federal University of Rio Grande (FURG), Dept. of Physics, Av. Italia, Km 8, Rio Grande, RS 96201-900 Brazil
AU: Signorini, S
EM: sergio@simbios.gsfc.nasa.gov
AF: NASA Goddard Space Flight Center, Mail Code 970.2, Greenbelt Road, Greenbelt, MD 20771 United States
AU: McClain, C R
EM: Charles.R.McClain@nasa.gov
AF: NASA Goddard Space Flight Center, Mail Code 970.2, Greenbelt Road, Greenbelt, MD 20771 United States
AB: Efforts have been made over the past decade to study bio-optical properties of seawater in the Southwestern Atlantic for mapping chlorophyll concentration from space. Coastal regions deserve a greater attention due to the optical complexity from continental influence. Here we present an attempt to derive reliable bio-optical chlorophyll algorithms in the shelf region 25-40^o S and 60-45^o W. This area is subject to large optical interference by continental runoffs from La Plata River and Patos Lagoon. Spectral upwelling radiance and surface chlorophyll concentration data have been collected in the past years and have been used to generate a regional version of the NASA's OC2v4 model. The regional 2-band algorithm (termed OC2-LP), reduces chlorophyll positive bias to 11% as compared to the global SeaWiFS OC4v4 algorithm (bias = 27%). However, OC2-LP remains with an overall inaccuracy of over 40% in chlorophyll concentration, as calculated by the absolute percentage difference between in-situ and model-derived values. In-situ chlorophyll data from two cruises to the study region (La Plata I - winter of 2003 and La Plata II - summer of 2004) have been used to test the accuracy of the derived algorithm as well as the global version. A marked seasonal difference was found, where both OC4v4 and OC2-LP overestimate chlorophyll in summer at a higher magnitude than in the winter. These results indicate the need for other approaches rather than use of empirical band-ratio models in coastal waters of this region.
DE: 3360 Remote sensing
DE: 4219 Continental shelf processes
DE: 4815 Ecosystems, structure and dynamics
SC: Ocean Sciences [OS]
MN: 2005 Joint Assembly