New Zealand Journal of Marine and Freshwater Research abstracts
A method for estimating inherent optical properties of New Zealand continental
shelf waters from satellite ocean colour measurements
Matthew H. Pinkerton1
Gerald F. Moore2
Samantha J. Lavender3
Mark P. Gall4
Kadija Oubelkheir5
Kenneth M. Richardson1
Philip W. Boyd6
James Aiken2
1National Institute of Water and Atmospheric
Research Limited
Private Bag 14901, Kilbirnie
Wellington, New Zealand
email: m.pinkerton@niwa.co.nz
2Plymouth Marine Laboratory
Prospect Place
Plymouth, United Kingdom
3School of Earth, Ocean and Environmental
Sciences (SEOES)
University of Plymouth
Plymouth, United Kingdom
4National Institute of Water and Atmospheric
Research Limited
P.O. Box 8602
Christchurch, New Zealand
5Inland and Coastal Water Remote Sensing
Environmental Remote Sensing Group
CSIRO Land & Water
GPO Box 1666, Canberra
ACT 2601 Australia
6National Institute of Water and Atmospheric
Research Limited
Centre for Chemical and Physical Oceanography
Department of Chemistry
University of Otago
Dunedin, New Zealand
Abstract We describe a method to estimate spectral absorption
and backscattering coefficients between 412 and 555 nm from measurements of
remote sensing reflectance across the visible spectrum. The algorithm described
is applicable to ocean colour satellite measurements (e.g., SeaWiFS). In situ measurements
of inherent and apparent optical properties were made at 19 coastal stations
off the north coast of New Zealand’s South Island in December 2001. These
measurements were used to parameterise a bio-optical model that estimates remote
sensing reflectance from concentrations of water constituents. The model generated
a large number (5000) of modelled ocean colour reflectance spectra that represented
a greater range of biogeochemical conditions than were measured in the study
area. These modelled values spanned a wide range of chlorophyll concentrations
(0.1–10 mg m–3), total suspended particulate material concentrations
(0.1–50 g m–3), and dissolved yellow substance absorptions (0.01–3
m–1). The modelled spectra were then used to test the performance of the
algorithm. The median ratio of algorithm values to target values was 0.84 (absorption),
and 0.80 (backscatter), and the median absolute errors were 33% (absorption)
and 36% (backscatter) across two orders of magnitude. The r2 values
between target and algorithm values of inherent optical properties in log-log
space were 0.89 for backscatter, and varied with wavelength for absorption
from 0.79 (412 nm), 0.72 (443 nm), 0.63 (490 nm), 0.55 (510 nm), and 0.21 (555
nm).
Keywords SeaWiFS; MODIS; ocean colour; remote sensing; bio-optical
algorithm; New Zealand; case 2
New Zealand Journal of Marine and Freshwater Research, 2006, Vol. 40:
227–247
0028–8330/06/4002–0227 © The Royal Society
of New Zealand 2006
M05028; Online publication date 10 April 2006. Received 19 May 2005;
accepted 21 November 2005
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