View Abstract

CHLOROPHYLL RETRIEVAL ALGORITHMS AND EFFECTS OF HIGHLY VARIABLE TSS AND CDOM USING A LARGE SPECTRAL LIBRARY OF INLAND AND COASTAL OBSERVATIONS

Since 1996, we’ve used consistent procedures to measure water reflectance (n > 980) and optically active and other constituents at stations in highly variable conditions of lakes and reservoirs, freshwater rivers and their estuaries, and coastal and deep oceans. Prior to 2002, we used an Ocean Optics ST1000 spectrophotometer for water reflectance, normalized with a spectralon panel. All measures since (~80% of our measurements) used a cross-calibrated pair of Ocean Optics USB 2000 spectrometers for solar downwelling and water signals. Major optical constituents varied by 4 to 5 orders of magnitude (chlorophyll a ranged from 0.04 – 490 mg/m3, total suspended sediments from 0.2 – 726 mg/L, and CDOM (abs 440 nm, 0.01 – 21.1 per m) and had low intracorrelations. These conditions provided a robust test bed for comparing chlorophyll retrieval algorithms and assessing impacts of non-algal constituents. Algorithms using higher visible and near-infrared bands, developed for turbid Case 2 waters, performed very well (r2 values > 0.85) across the range of measurements. These algorithms use band combinations that effectively normalize for TSS and CDOM, although residual analysis reveals the variable influences of higher amounts of these two variables. In general, the salinity of a station had minimal influence on our results, indicating ability to use these approaches in a wide array of surface waters. A critique of the applicability of retrieval procedures and case examples of their applications with aerial and space-borne hyperspectral instruments will be presented.

Authors

Schalles, J. F., Creighton University, USA, JohnSchalles@creighton.edu

Hladik, C. M., Georgia Southern University, USA, chladik@georgiasouthern.edu

Yacobi, Y. Z., Kinneret Limnological Laboratory, Israel, yzy@ocean.org.il

Olley, J. T., Creighton University, USA, JohnOlley@creighton.edu

O'Donnell, J. P., Creighton University, USA, JohnODonnell@creighton.edu

Details

Oral presentation

Session #:031
Date: 02/28/2017
Time: 12:30
Location: 323 A

Presentation is given by student: No