DOI: 10.5194/bg-17-475-2020
论文题名: A global end-member approach to derive <i>a</i>CDOM(440) from near-surface optical measurements
作者: Hooker S.B. ; Matsuoka A. ; Kudela R.M. ; Yamashita Y. ; Suzuki K. ; Houskeeper H.F.
刊名: Biogeosciences
ISSN: 17264170
出版年: 2020
卷: 17, 期: 2 语种: 英语
Scopus关键词: absorption coefficient
; cluster analysis
; global perspective
; observational method
; optical property
; turbidity
; water mass
; Arctic Ocean
; Hawaii
; Hawaii [United States]
; Japan
; Pacific Ocean
; Pacific Ocean (North)
; Puerto Rico
; United States
英文摘要: This study establishes an optical inversion scheme for deriving the absorption coefficient of colored (or chromophoric, depending on the literature) dissolved organic material (CDOM) at the 440 nm wavelength, which can be applied to global water masses with near-equal efficacy. The approach uses a ratio of diffuse attenuation coefficient spectral end-members, i.e., a short- and long-wavelength pair. The global perspective is established by sampling "extremely" clear water plus a generalized extent in turbidity and optical properties that each span 3 decades of dynamic range. A unique data set was collected in oceanic, coastal, and inland waters (as shallow as 0.6 m) from the North Pacific Ocean, the Arctic Ocean, Hawaii, Japan, Puerto Rico, and the western coast of the United States. The data were partitioned using subjective categorizations to define a validation quality subset of conservative water masses (i.e., the inflow and outflow of properties constrain the range in the gradient of a constituent) plus 15 subcategories of more complex water masses that were not necessarily evolving conservatively. The dependence on optical complexity was confirmed with an objective methodology based on a cluster analysis technique. The latter defined five distinct classes with validation quality data present in all classes, but which also decreased in percent composition as a function of increasing class number and optical complexity. Four algorithms based on different validation quality end-members were validated with accuracies of 1.2 %-6.2 %, wherein pairs with the largest spectral span were most accurate. Although algorithm accuracy decreased with the inclusion of more subcategories containing nonconservative water masses, changes to the algorithm fit were small when a preponderance of subcategories were included. The high accuracy for all end-member algorithms was the result of data acquisition and data processing improvements, e.g., increased vertical sampling resolution to less than 1mm (with pressure transducer precision of 0.03-0.08 mm) and a boundary constraint to mitigate wave-focusing effects, respectively. An independent evaluation with a historical database confirmed the consistency of the algorithmic approach and its application to quality assurance, e.g., to flag data outside expected ranges, identify suspect spectra, and objectively determine the in-water extrapolation interval by converging agreement for all applicable end-member algorithms. The legacy data exhibit degraded performance (as 44% uncertainty) due to a lack of high-quality near-surface observations, especially for clear waters wherein wave-focusing effects are problematic. The novel optical approach allows the in situ estimation of an inwater constituent in keeping with the accuracy obtained in the laboratory. © Author(s) 2020. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/159985
Appears in Collections: 气候变化与战略
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作者单位: Ocean Ecology Laboratory/Code 616.2, NASA Goddard Space Flight Center, Greenbelt, MD 20771, United States; Takuvik Joint International Laboratory, Université Laval, Québec City, G1V 0A6, Canada; Ocean Sciences Department, University of California Santa Cruz, Santa Cruz, CA 95064, United States; Faculty of Environmental Earth Science, Hokkaido University, Sapporo, 060-0810, Japan
Recommended Citation:
Hooker S.B.,Matsuoka A.,Kudela R.M.,et al. A global end-member approach to derive <i>a</i>CDOM(440) from near-surface optical measurements[J]. Biogeosciences,2020-01-01,17(2)