Improvements to PhytoDOAS method for identification of major phytoplankton groups using high spectrally resolved satellite data.


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Astrid.Bracher [ at ] awi.de

Abstract

The goal of this study was to improve AS, which is a new retrieval method for quantitaidentification of major Phytoplankton Functional Types using hyper-spectral satellite data. PhytoDOAS is of the Differential Optical Absorption Spec(DOAS, a method for detection of atmospheric trace eloped for remote identification of oceanic phygroups. Thus far, PhytoDOAS has been sucxploited to identify cyanobacteria and diatoms global ocean from SCIAMACHY (SCanning ImagAbsorption spectroMeter for Atmospheric CartograpHY) -spectral data. The main challenge for retrieving more ytoDOAS is to overcome the correlation efbetween different PFTs’ absorption spectra. Differare composed of different types and amounts of ut also have pigments in common, e.g., chl-a, correlation effects in the usual performance of the retrieval. Two ideas have been implemented to ytoDOAS for the PFT retrieval of more phytogroups. Firstly, using the fourth-derivative specthe peak positions of the main pigment compoeach absorption spectrum have been derived. Afcomparing the corresponding results of major PFTs, the fit-window for the PhytoDOAS retrieval of each determined. Secondly, based on the results from spectroscopy, simultaneous fit of PhytoDOAS has proposed and tested for a selected set of PFTs (coccoldiatoms and dinoflagllates) within an optimized The method was then applied to the processSCIAMACHY data over the year 2005. Comparisons ytoDOAS PFT retrievals in 2005 with the moddata from the NASA Ocean Biochemical Model showed similar patterns in their seasonal distridiatoms and coccolithophores, especially in thenorthern parts of the global ocean. The seasonal patterns of the PhytoDOAS coccolithophores indicated very good agreement with the global distributions of Particulate Inorganic Carbon (PIC) provided by MODIS (MODerate resolution Imaging Spectroradiometer)-Aqua level-3 products. Since PIC is known as a proxy for the abundance of coccolithophores (in open ocean), the latter agreement indicates the basic functionality of the method in retrieving coccolithophores. Moreover, as a case study, the simultaneous mode of PhytoDOAS has been applied to SCIAMACHY data for detecting a coccolithophore bloom around New Zealand (reported by NASA from MODIS imagery in December 2009); the result was quite consistent with the MODIS RGB image and the MODIS PIC map of the bloom, indicating the functionality of the method in short-term retrievals.



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Article
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Not peer-reviewed
Publication Status
Published
Eprint ID
25493
DOI 10.5194/osd-8-2271-2011

Cite as
Sadeghi, A. , Dinter, T. , Vountas, M. , Taylor, B. , Peeken, I. and Bracher, A. (2011): Improvements to PhytoDOAS method for identification of major phytoplankton groups using high spectrally resolved satellite data. , Ocean Science, 8 , pp. 2313-2376 . doi: 10.5194/osd-8-2271-2011


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