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Use of remote-sensing reflectance to constrain a data assimilating marine biogeochemical model of the Great Barrier Reef

Citation

Jones, EM and Baird, ME and Mongin, M and Parslow, J and Skerratt, J and Lovell, J and Margvelashvili, N and Matear, RJ and Wild-Allen, K and Robson, B and Rizwi, F and Oke, P and King, E and Schroeder, T and Steven, A and Taylor, J, Use of remote-sensing reflectance to constrain a data assimilating marine biogeochemical model of the Great Barrier Reef, Biogeosciences, 13, (23) pp. 6441-6469. ISSN 1726-4170 (2016) [Refereed Article]


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Copyright 2016 Authors. Licensed under Creative Commons Attribution 3.0 Unported (CC BY 3.0) https://creativecommons.org/licenses/by/3.0/

DOI: doi:10.5194/bg-13-6441-2016

Abstract

Skillful marine biogeochemical (BGC) models are required to understand a range of coastal and global phenomena such as changes in nitrogen and carbon cycles. The refinement of BGC models through the assimilation of variables calculated from observed in-water inherent optical properties (IOPs), such as phytoplankton absorption, is problematic. Empirically derived relationships between IOPs and variables such as chlorophyll-a concentration (Chl a), total suspended solids (TSS) and coloured dissolved organic matter (CDOM) have been shown to have errors that can exceed 100% of the observed quantity. These errors are greatest in shallow coastal regions, such as the Great Barrier Reef (GBR), due to the additional signal from bottom reflectance. Rather than assimilate quantities calculated using IOP algorithms, this study demonstrates the advantages of assimilating quantities calculated directly from the less error-prone satellite remote-sensing reflectance (RSR). To assimilate the observed RSR, we use an in-water optical model to produce an equivalent simulated RSR and calculate the mismatch between the observed and simulated quantities to constrain the BGC model with a deterministic ensemble Kalman filter (DEnKF). The traditional assumption that simulated surface Chl a is equivalent to the remotely sensed OC3M estimate of Chl a resulted in a forecast error of approximately 75 %. We show this error can be halved by instead using simulated RSR to constrain the model via the assimilation system. When the analysis and forecast fields from the RSR-based assimilation system are compared with the non-assimilating model, a comparison against independent in situ observations of Chl a, TSS and dissolved inorganic nutrients (NO3, NH4 and DIP) showed that errors are reduced by up to 90 %. In all cases, the assimilation system improves the simulation compared to the non-assimilating model. Our approach allows for the incorporation of vast quantities of remote-sensing observations that have in the past been discarded due to shallow water and/or artefacts introduced by terrestrially derived TSS and CDOM or the lack of a calibrated regional IOP algorithm.

Item Details

Item Type:Refereed Article
Keywords:remote sensing, reflectance, marine biogeochemical model, Great Barrier Reef, data assimilating, marine biogeochemistry
Research Division:Earth Sciences
Research Group:Oceanography
Research Field:Chemical Oceanography
Objective Division:Environment
Objective Group:Physical and Chemical Conditions of Water
Objective Field:Physical and Chemical Conditions of Water in Marine Environments
UTAS Author:Baird, ME (Dr Mark Baird)
UTAS Author:Mongin, M (Mr Mathieu Mongin)
UTAS Author:Matear, RJ (Dr Richard Matear)
UTAS Author:Oke, P (Dr Peter Oke)
ID Code:118282
Year Published:2016
Web of Science® Times Cited:19
Deposited By:Directorate
Deposited On:2017-07-10
Last Modified:2018-05-09
Downloads:94 View Download Statistics

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