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  • 1
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    Atmospheric and Surface Processes, and Feedback Mechanisms Determining Arctic Amplification: A Review of First Results and Prospects of the (AC)3 Project
    American Meteorological Society ; 2023
    In:  Bulletin of the American Meteorological Society Vol. 104, No. 1 ( 2023-01), p. E208-E242
    Details
    In: Bulletin of the American Meteorological Society, American Meteorological Society, Vol. 104, No. 1 ( 2023-01), p. E208-E242
    Abstract: Mechanisms behind the phenomenon of Arctic amplification are widely discussed. To contribute to this debate, the (AC) 3 project was established in 2016 ( www.ac3-tr.de/ ). It comprises modeling and data analysis efforts as well as observational elements. The project has assembled a wealth of ground-based, airborne, shipborne, and satellite data of physical, chemical, and meteorological properties of the Arctic atmosphere, cryosphere, and upper ocean that are available for the Arctic climate research community. Short-term changes and indications of long-term trends in Arctic climate parameters have been detected using existing and new data. For example, a distinct atmospheric moistening, an increase of regional storm activities, an amplified winter warming in the Svalbard and North Pole regions, and a decrease of sea ice thickness in the Fram Strait and of snow depth on sea ice have been identified. A positive trend of tropospheric bromine monoxide (BrO) column densities during polar spring was verified. Local marine/biogenic sources for cloud condensation nuclei and ice nucleating particles were found. Atmospheric–ocean and radiative transfer models were advanced by applying new parameterizations of surface albedo, cloud droplet activation, convective plumes and related processes over leads, and turbulent transfer coefficients for stable surface layers. Four modes of the surface radiative energy budget were explored and reproduced by simulations. To advance the future synthesis of the results, cross-cutting activities are being developed aiming to answer key questions in four focus areas: lapse rate feedback, surface processes, Arctic mixed-phase clouds, and airmass transport and transformation.
    Type of Medium: Online Resource
    ISSN: 0003-0007 , 1520-0477
    URL: Article
    URL: Article
    DOI: 10.1175/BAMS-D-21-0218.1
    DOI: 10.1175/BAMS-D-21-0218.2
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2023
    detail.hit.zdb_id: 2029396-3
    detail.hit.zdb_id: 419957-1
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  • 2
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    Improvement to the PhytoDOAS method for identification of coccolithophores using hyper-spectral satellite data
    Copernicus GmbH ; 2012
    In:  Ocean Science Vol. 8, No. 6 ( 2012-11-30), p. 1055-1070
    Details
    In: Ocean Science, Copernicus GmbH, Vol. 8, No. 6 ( 2012-11-30), p. 1055-1070
    Abstract: Abstract. The goal of this study was to improve PhytoDOAS, which is a new retrieval method for quantitative identification of major phytoplankton functional types (PFTs) using hyper-spectral satellite data. PhytoDOAS is an extension of the Differential Optical Absorption Spectroscopy (DOAS, a method for detection of atmospheric trace gases), developed for remote identification of oceanic phytoplankton groups. Thus far, PhytoDOAS has been successfully exploited to identify cyanobacteria and diatoms over the global ocean from SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) hyper-spectral data. This study aimed to improve PhytoDOAS for remote identification of coccolithophores, another functional group of phytoplankton. The main challenge for retrieving more PFTs by PhytoDOAS is to overcome the correlation effects between different PFT absorption spectra. Different PFTs are composed of different types and amounts of pigments, but also have pigments in common, e.g. chl a, causing correlation effects in the usual performance of the PhytoDOAS retrieval. Two ideas have been implemented to improve PhytoDOAS for the PFT retrieval of more phytoplankton groups. Firstly, using the fourth-derivative spectroscopy, the peak positions of the main pigment components in each absorption spectrum have been derived. After comparing the corresponding results of major PFTs, the optimized fit-window for the PhytoDOAS retrieval of each PFT was determined. Secondly, based on the results from derivative spectroscopy, a simultaneous fit of PhytoDOAS has been proposed and tested for a selected set of PFTs (coccolithophores, diatoms and dinoflagellates) within an optimized fit-window, proven by spectral orthogonality tests. The method was then applied to the processing of SCIAMACHY data over the year 2005. Comparisons of the PhytoDOAS coccolithophore retrievals in 2005 with other coccolithophore-related data showed similar patterns in their seasonal distributions, especially in the North Atlantic and the Arctic Sea. The seasonal patterns of the PhytoDOAS coccolithophores indicated very good agreement with the coccolithophore modeled data from the NASA Ocean Biochemical Model (NOBM), as well as with the global distributions of particulate inorganic carbon (PIC), provided by MODIS (MODerate resolution Imaging Spectroradiometer)-Aqua level-3 products. Moreover, regarding the fact that coccolithophores belong to the group of haptophytes, the PhytoDOAS seasonal coccolithophores showed good agreement with the global distribution of haptophytes, derived from synoptic pigment relationships applied to SeaWiFS chl a. As a case study, the simultaneous mode of PhytoDOAS has been applied to SCIAMACHY data for detecting a coccolithophore bloom which was consistent with the MODIS RGB image and the MODIS PIC map of the bloom, indicating the functionality of the method also in short-term retrievals.
    Type of Medium: Online Resource
    ISSN: 1812-0792
    URL: Article
    URL: Article
    DOI: 10.5194/os-8-1055-2012
    DOI: 10.5194/os-8-1055-2012-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2012
    detail.hit.zdb_id: 2183769-7
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  • 3
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    Global retrieval of marine and terrestrial chlorophyll fluorescence at its red peak using hyperspectral top of atmosphere radiance measurements: Feasibility study and first results
    Elsevier BV ; 2015
    In:  Remote Sensing of Environment Vol. 166 ( 2015-09), p. 243-261
    Details
    In: Remote Sensing of Environment, Elsevier BV, Vol. 166 ( 2015-09), p. 243-261
    Type of Medium: Online Resource
    ISSN: 0034-4257
    URL: Article
    DOI: 10.1016/j.rse.2015.05.018
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2015
    detail.hit.zdb_id: 1498713-2
    SSG: 11
    SSG: 14
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  • 4
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    Remote sensing of coccolithophore blooms in selected oceanic regions using the PhytoDOAS method applied to hyper-spectral satellite data
    Copernicus GmbH ; 2012
    In:  Biogeosciences Vol. 9, No. 6 ( 2012-06-14), p. 2127-2143
    Details
    In: Biogeosciences, Copernicus GmbH, Vol. 9, No. 6 ( 2012-06-14), p. 2127-2143
    Abstract: Abstract. In this study temporal variations of coccolithophore blooms are investigated using satellite data. Eight years (from 2003 to 2010) of data of SCIAMACHY, a hyper-spectral satellite sensor on-board ENVISAT, were processed by the PhytoDOAS method to monitor the biomass of coccolithophores in three selected regions. These regions are characterized by frequent occurrence of large coccolithophore blooms. The retrieval results, shown as monthly mean time series, were compared to related satellite products, including the total surface phytoplankton, i.e. total chlorophyll a (from GlobColour merged data) and the particulate inorganic carbon (from MODIS-Aqua). The inter-annual variations of the phytoplankton bloom cycles and their maximum monthly mean values have been compared in the three selected regions to the variations of the geophysical parameters: sea-surface temperature (SST), mixed-layer depth (MLD) and surface wind-speed, which are known to affect phytoplankton dynamics. For each region, the anomalies and linear trends of the monitored parameters over the period of this study have been computed. The patterns of total phytoplankton biomass and specific dynamics of coccolithophore chlorophyll a in the selected regions are discussed in relation to other studies. The PhytoDOAS results are consistent with the two other ocean color products and support the reported dependencies of coccolithophore biomass dynamics on the compared geophysical variables. This suggests that PhytoDOAS is a valid method for retrieving coccolithophore biomass and for monitoring its bloom developments in the global oceans. Future applications of time series studies using the PhytoDOAS data set are proposed, also using the new upcoming generations of hyper-spectral satellite sensors with improved spatial resolution.
    Type of Medium: Online Resource
    ISSN: 1726-4189
    URL: Article
    DOI: 10.5194/bg-9-2127-2012
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2012
    detail.hit.zdb_id: 2158181-2
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  • 5
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    DETERMINATION OF PHYTOPLANKTON CONCENTRATIONS FROM SPACE-BORNE SPECTROSCOPIC MEASUREMENTS
    SciELO Agencia Nacional de Investigacion y Desarrollo (ANID) ; 2004
    In:  Gayana (Concepción) Vol. 68, No. 2 ( 2004)
    Details
    In: Gayana (Concepción), SciELO Agencia Nacional de Investigacion y Desarrollo (ANID), Vol. 68, No. 2 ( 2004)
    Type of Medium: Online Resource
    ISSN: 0717-6538
    URL: Article
    DOI: 10.4067/S0717-65382004000300039
    Language: English
    Publisher: SciELO Agencia Nacional de Investigacion y Desarrollo (ANID)
    Publication Date: 2004
    detail.hit.zdb_id: 2105402-2
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  • 6
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    Quantitative observation of cyanobacteria and diatoms from space using PhytoDOAS on SCIAMACHY data
    Copernicus GmbH ; 2009
    In:  Biogeosciences Vol. 6, No. 5 ( 2009-05-06), p. 751-764
    Details
    In: Biogeosciences, Copernicus GmbH, Vol. 6, No. 5 ( 2009-05-06), p. 751-764
    Abstract: Abstract. In this study the technique of Differential Optical Absorption Spectroscopy (DOAS) has been adapted for the retrieval of the absorption and biomass of two major phytoplankton groups (PhytoDOAS) from data of the Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) satellite sensor. SCIAMACHY measures back scattered solar radiation in the UV-Vis-NIR spectral regions with a high spectral resolution (0.2 to 1.5 nm). In order to identify phytoplankton absorption characteristics in the SCIAMACHY data in the range of 430 to 500 nm, phytoplankton absorption spectra measured in-situ during two different RV "Polarstern" expeditions were used. The two spectra have been measured in different ocean regions where different phytoplankton groups (cyanobacteria and diatoms) dominated the phytoplankton composition. Results clearly show distinct absorption characteristics of the two phytoplankton groups in the SCIAMACHY spectra. Using these results in addition to calculations of the light penetration depth derived from DOAS retrievals of the inelastic scattering (developed by Vountas et al., 2007), globally distributed pigment concentrations for these characteristic phytoplankton groups for two monthly periods (February–March 2004 and October–November 2005) were determined. This satellite information on cyanobacteria and diatoms distribution clearly matches the concentrations based on high pressure liquid chromatography (HPLC) pigment analysis of collocated water samples and concentrations derived from a global model analysis with the NASA Ocean Biogeochemical Model (Gregg et al., 2003; Gregg and Casey 2007). The quantitative assessment of the distribution of key phytoplankton groups from space enables various biogeochemical regions to be distinguished and will be of great importance for the global modeling of marine ecosystems and biogeochemical cycles which enables the impact of climate change in the oceanic biosphere to be estimated.
    Type of Medium: Online Resource
    ISSN: 1726-4189
    URL: Article
    DOI: 10.5194/bg-6-751-2009
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2009
    detail.hit.zdb_id: 2158181-2
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  • 7
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    Online Resource
    Spectral studies of ocean water with space-borne sensor SCIAMACHY using Differential Optical Absorption Spectroscopy (DOAS)
    Copernicus GmbH ; 2007
    In:  Ocean Science Vol. 3, No. 3 ( 2007-09-26), p. 429-440
    Details
    In: Ocean Science, Copernicus GmbH, Vol. 3, No. 3 ( 2007-09-26), p. 429-440
    Abstract: Abstract. Methods enabling the retrieval of oceanic parameter from the space borne instrumentation Scanning Imaging Absorption Spectrometer for Atmospheric ChartographY (SCIAMACHY) using Differential Optical Absorption Spectroscopy (DOAS) are presented. SCIAMACHY onboard ENVISAT measures back scattered solar radiation at a spectral resolution (0.2 to 1.5 nm). The DOAS method was used for the first time to fit modelled Vibrational Raman Scattering (VRS) in liquid water and in situ measured phytoplankton absorption reference spectra to optical depths measured by SCIAMACHY. Spectral structures of VRS and phytoplankton absorption were clearly found in these optical depths. Both fitting approaches lead to consistent results. DOAS fits correlate with estimates of chlorophyll concentrations: low fit factors for VRS retrievals correspond to large chlorophyll concentrations and vice versa; large fit factors for phytoplankton absorption correspond with high chlorophyll concentrations and vice versa. From these results a simple retrieval technique taking advantage of both measurements is shown. First maps of global chlorophyll concentrations were compared to the corresponding MODIS measurements with very promising results. In addition, results from this study will be used to improve atmospheric trace gas DOAS-retrievals from visible wavelengths by including these oceanographic signatures.
    Type of Medium: Online Resource
    ISSN: 1812-0792
    URL: Article
    DOI: 10.5194/os-3-429-2007
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2007
    detail.hit.zdb_id: 2183769-7
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  • 8
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    Corrigendum to "Spectral studies of ocean water with space-borne sensor SCIAMACHY using Differential Optical Absorption Spectroscopy (DOAS)" published in Ocean Sci., 3, 429–440, 2007
    Copernicus GmbH ; 2007
    In:  Ocean Science Vol. 3, No. 4 ( 2007-10-19), p. 483-483
    Details
    In: Ocean Science, Copernicus GmbH, Vol. 3, No. 4 ( 2007-10-19), p. 483-483
    Type of Medium: Online Resource
    ISSN: 1812-0792
    URL: Article
    DOI: 10.5194/os-3-483-2007
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2007
    detail.hit.zdb_id: 2183769-7
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