The Observation, Modeling, and Retrieval of Bio-Optical Properties for Coastal Waters of the Southern Chesapeake Bay

<p>The primary purpose of this study was to develop an inverse method to retrieve the inherent optical properties (IOPs) and biogeochemical parameters (e.g. chlorophyll <em>a</em> concentration and salinity) appropriate to monitor the water quality and biogeochemical processes from remote sensing of the coastal waters in the southern Chesapeake Bay and coastal Mid-Atlantic Bight region (MAB) dominated by Case 2 waters. For this purpose, knowledge of the relationship between remote sensing reflectance (<em>R_rs</em>) and IOPs and the effect from bottom reflectance on <em>R_rs</em>, is required.</p> <p>A substantial investigation of IOPs has been conducted for the coastal waters of the southern Chesapeake Bay. Although phytoplankton are the dominant contributors to IOPs of oceanic Case 1 waters, colored dissolved organic matter (CDOM) derived from non-phytoplankton sources and sedimentary particles also play very important roles in coastal Case 2 waters. Strongly influenced by riverine discharge, the shallow coastal waters of the southern Chesapeake Bay provide challenges and opportunities to develop regionally specific IOP retrieval methods from remotely sensed ocean color imagery.</p> <p>A semi-analytical radiative transfer model (PZ06_<em>E_d</em>), based on the analysis of the simulated results of an exact radiative transfer model, <em>Hydrolight</em>® [<em>Mobley</em>, 1994], was developed to estimate the vertical distribution of downwelling plane irradiance [<em>E_d</em>(<em>z</em>)] from IOPs and sky conditions (e.g. cloud coverage and solar zenith angle). Compared to the significant overestimation of the simple <em>Gordon</em> [1989] model for particle-rich environments, PZ06_<em>Ed</em> agreed with <em>Hydrolight</em>® with < 6% of the root-mean-square (RMS) error. Field observations from the coastal waters of the southern Chesapeake Bay validated the predictions of PZ06_<em> Ed</em>with RMS error from 10% to 14%. The SeaWiFS imagery of the diffuse attenuation coefficient (<em>K_d</em>) estimated from PZ06_<em>E_d</em> is significantly improved from the <em>Mueller</em> [2000] model and displays obviously the coastal processes in the lower MAB, including the riverine outflow from the Chesapeake Bay and the mixing of the Gulf Stream with the local waters.</p> <p>The quadratic model (e.g. GSMO1) describing <em>R_rs</em> and IOPs has been widely used in bio-optics to retrieve inherent optical properties (IOPs). In this study, the derived coefficients (<em>l₁</em> and <em>l₂</em>) by <em>Gordon et al.</em> [1988] were re-evaluated from <em>Hydrolight</em>® simulations and incorporated into a semi-analytical radiative transfer model (PZ06_<em> R_rs</em>) that included bottom effects for optically shallow waters. Compared with <em>Hydrolight</em>® simulations and field observations in the Chesapeake Light Tower (CLT), <em>R_rs</em> calculated from PZ06_<em>Rrs</em> typically agreed within 5% and about 7% to 13% of RMS, respectively. <em>Hydrolight </em>® simulations and field observations also confirmed that PZ06_<em>R_rs</em> improved the retrieval of biogeochemical-related parameters, including [Chl], <em>a_dg</em>(443), and <em>b_bp</em>(443), compared to global ocean color algorithms (e.g. OC3M) and semi-analytic models without considering the bottom effects (e.g. GSM01-CLT).</p> <p>Finally, the relatively successful inverse modeling provides a promising method to study ecosystem-level biogeochemical and physical parameters from remote sensing for coastal waters of southern Chesapeake Bay and even lower MAB.</p>

Name thesis:degree_name

Doctor of Philosophy (PhD)

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Ocean & Earth Sciences

Year dc:date.available

2007

Author dc:creator

• Pan, Xiaoju

Contributors dc:contributor

• Richard C. Zimmerman
• Larry P. Atkinson
• Margaret R. Mulholland
• Zhonghai Jin
• Mark Havey

• Chesapeake Bay
• Coastal waters
• Dissolved organic matter
• Phytoplankton
• Biogeochemistry
• Oceanography

Statement dc:rights

• <p>In Copyright. URI: <a href="http://rightsstatements.org/vocab/InC/1.0/">http://rightsstatements.org/vocab/InC/1.0/</a> This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).</p>

Identifier

9780549069546

OAI identifier oai:identifier

oai:digitalcommons.odu.edu:oeas_etds-1063