ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    facet.materialart.
    Unknown
    Improving estimates of Gross Primary Productivity by assimilating solar‐induced fluorescence satellite retrievals in a terrestrial biosphere model using a process‐based SIF model (2019)
    Wiley
    Details
    Publication Date: 2019
    Description: Abstract Over the last few years, solar‐induced chlorophyll fluorescence (SIF) observations from space have emerged as a promising resource for evaluating the spatio‐temporal distribution of gross primary productivity (GPP) simulated by global terrestrial biosphere models (TBMs). SIF can be used to improve GPP simulations by optimizing critical model parameters through statistical Bayesian data assimilation techniques. A prerequisite is the availability of a functional link between GPP and SIF in TBMs. Here, we present the development of a mechanistic SIF observation operator in the ORCHIDEE TBM. It simulates the regulation of photosystem II fluorescence quantum yield at the leaf level thanks to a novel parameterization of non‐photochemical quenching as a function of temperature, photosynthetically active radiation and normalized quantum yield of photochemistry. It emulates the radiative transfer of chlorophyll fluorescence to the top of the canopy using a parametric simplification of the SCOPE model. We assimilate two years of monthly OCO‐2 SIF product at 0.5° (2015‐2016) to optimize ORCHIDEE photosynthesis and phenological parameters over an ensemble of grid points for all plant functional types (PFTs). The impact on the simulated GPP is considerable with a large decrease of the global scale budget by 28 GtC.yr‐1 over the period 1990‐2009. The optimized GPP budget (134/135 GtC.yr‐1 over 1990‐2009/2001‐2009) remarkably agrees with independent GPP estimates, FLUXSAT 137 GtC.yr‐1 over 2001‐2009) in particular and FLUXCOM (121 GtC.yr‐1 over 1990‐2009). Our results also suggest a biome dependency of the SIF‐GPP relationship that needs to be improved for some PFTs.
    Print ISSN: 2169-8953
    Electronic ISSN: 2169-8961
    Topics: Biology , Geosciences
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 2
    facet.materialart.
    Unknown
    Space-based Remote Imaging Spectroscopy of the Aliso Canyon CH4 Super-emitter (2016)
    Wiley
    Details
    Publication Date: 2016-05-29
    Description: The Aliso Canyon gas storage facility near Porter Ranch California produced a large accidental CH 4 release from October 2015 to February 2016. The Hyperion imaging spectrometer onboard the EO-1 satellite successfully detected this event, achieving the first orbital attribution of CH 4 to a single anthropogenic super-emitter. Hyperion measured shortwave infrared signatures of CH 4 near 2.3  μ m at 0.01  μ m spectral resolution and 30 m spatial resolution. It detected the plume on three overpasses, mapping its magnitude and morphology. These orbital observations were consistent with measurements by airborne instruments. We evaluate Hyperion instrument performance, draw implications for future orbital instruments, and extrapolate the potential for a global survey of CH 4 super-emitters.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 3
    facet.materialart.
    Unknown
    Disentangling chlorophyll fluorescence from atmospheric scattering effects in O2 A-band spectra of reflected sun-light (2011)
    Wiley
    Details
    Publication Date: 2011-02-01
    Description: Global retrieval of solar induced fluorescence emitted by terrestrial vegetation can provide an unprecedented measure for photosynthetic efficiency. The GOSAT (JAXA, launched Feb. 2009) and OCO-2 (NASA, to be launched 2013) satellites record high-resolution spectra in the O2 A-band region, overlapping part of the chlorophyll fluorescence spectrum. We show that fluorescence cannot be unambiguously discriminated from atmospheric scattering effects using O2 absorption lines. This can cause systematic biases in retrieved scattering parameters (aerosol optical thickness, aerosol height, surface pressure, surface albedo) if fluorescence is neglected. Hence, we demonstrate an efficient alternative fluorescence least-squares retrieval method based solely on strong Fraunhofer lines in the vicinity of the O2 A-band, disentangling fluorescence from scattering effects. Not only does the Fraunhofer line fit produce a more accurate estimate of fluorescence emission, but it also allows improved retrievals of atmospheric aerosols from the O2 A-band.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 4
    facet.materialart.
    Unknown
    Global column-averaged methane mixing ratios from 2003 to 2009 as derived from SCIAMACHY: Trends and variability (2011)
    Wiley
    Details
    Publication Date: 2011-02-17
    Description: After a decade of stable or slightly decreasing global methane concentrations, ground-based in situ data show that CH4 began increasing again in 2007 and that this increase continued through 2009. So far, space-based retrievals sensitive to the lower troposphere in the time period under consideration have not been available. Here we report a long-term data set of column-averaged methane mixing ratios retrieved from spectra of the Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) instrument onboard Envisat. The retrieval quality after 2005 was severely affected by degrading detector pixels within the methane 2ν3 absorption band. We identified the most crucial problems in SCIAMACHY detector degradation and overcame the problem by applying a strict pixel mask as well as a new dark current characterization. Even though retrieval precision after the end of 2005 is invariably degraded, consistent methane retrievals from 2003 through 2009 are now possible. Regional time series in the Sahara, Australia, tropical Africa, South America, and Asia show the methane increase in 2007–2009, but we cannot yet draw a firm conclusion concerning the origin of the increase. Tropical Africa even seems to exhibit a negative anomaly in 2006, but an impact from changes in SCIAMACHY detector degradation cannot be excluded yet. Over Assakrem, Algeria, we observed strong similarities between SCIAMACHY measurements and ground-based data in deseasonalized time series. We further show long-term SCIAMACHY xCH4 averages at high spatial resolution that provide further insight into methane variations on regional scales. The Red Basin in China exhibits, on average, the highest methane abundance worldwide, while other localized features such as the Sudd wetlands in southern Sudan can also be identified in SCIAMACHY xCH4 averages.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 5
    facet.materialart.
    Unknown
    Toward accurate CO2 and CH4 observations from GOSAT (2011)
    Wiley
    Details
    Publication Date: 2011-07-30
    Description: The column-average dry air mole fractions of atmospheric carbon dioxide and methane (XCO2 and XCH4) are inferred from observations of backscattered sunlight conducted by the Greenhouse gases Observing SATellite (GOSAT). Comparing the first year of GOSAT retrievals over land with colocated ground-based observations of the Total Carbon Column Observing Network (TCCON), we find an average difference (bias) of −0.05% and −0.30% for XCO2 and XCH4 with a station-to-station variability (standard deviation of the bias) of 0.37% and 0.26% among the 6 considered TCCON sites. The root-mean square deviation of the bias-corrected satellite retrievals from colocated TCCON observations amounts to 2.8 ppm for XCO2 and 0.015 ppm for XCH4. Without any data averaging, the GOSAT records reproduce general source/sink patterns such as the seasonal cycle of XCO2 suggesting the use of the satellite retrievals for constraining surface fluxes.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 6
    facet.materialart.
    Unknown
    Sustained Non‐Photochemical Quenching Shapes the Seasonal Pattern of Solar‐ Induced Fluorescence at a High‐Elevation Evergreen Forest (2019)
    Wiley
    Details
    Publication Date: 2019
    Description: Abstract Traditional methods of carbon monitoring in mountainous regions are challenged by complex terrain. Recently, solar‐induced fluorescence (SIF) has been found to be an indicator of gross primary production (GPP), and the increased availability of remotely‐sensed SIF provides an opportunity to estimate GPP across the Western US. Although the empirical linkage between SIF and GPP is strong, the current mechanistic understanding of this linkage is incomplete, and depends upon changes in leaf biochemical processes in which absorbed sunlight leads to photochemistry, heat (via non‐photochemical quenching, NPQ), fluorescence, or tissue damage. An improved mechanistic understanding is necessary to leverage SIF observations to improve representation of ecosystem processes within land surface models. Here, we included an improved fluorescence model within the Community Land Model, Version 4.5 (CLM 4.5) to simulate seasonal changes in SIF at a subalpine forest in Colorado. We found that when the model accounted for sustained NPQ this provided a larger seasonal change in fluorescence yield leading to simulated SIF that more closely resembled the observed seasonal pattern (GOME‐2 satellite platform and a tower‐mounted spectrometer system). We found that an acclimation model based on mean air temperature was a useful predictor for sustained NPQ. Although light intensity was not an important factor for this analysis, it should be considered before applying the sustained NPQ and SIF to other cold climate evergreen biomes. More leaf level fluorescence measurements are necessary to better understand the seasonal relationship between sustained and reversible components of NPQ and to what extent that influences solar‐induced fluorescence.
    Print ISSN: 2169-8953
    Electronic ISSN: 2169-8961
    Topics: Biology , Geosciences
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 7
    facet.materialart.
    Unknown
    The seasonal variation of the CO2 flux over Tropical Asia estimated from GOSAT, CONTRAIL and IASI (2014)
    Wiley
    Details
    Publication Date: 2014-02-25
    Description: [1]  We estimate the CO 2 flux over Tropical Asia in 2009, 2010 and 2011 using GOSAT total column CO 2 (XCO 2 ) and in situ measurements of CO 2 . Compared to flux estimates from assimilating surface measurements of CO 2 , GOSAT XCO 2 estimates a more dynamic seasonal cycle and a large source in March – May 2010. The more dynamic seasonal cycle is consistent with earlier work by Patra et al . [2011], and the enhanced 2010 source is supported by independent upper air CO 2 measurements from the CONTRAIL project. Using IASI measurements of total column CO (XCO), we show that biomass burning CO 2 can explain neither the dynamic seasonal cycle nor the 2010 source. We conclude that both features must come from the terrestrial biosphere. In particular the 2010 source points to biosphere response to above-average temperatures that year.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 8
    facet.materialart.
    Unknown
    High‐Resolution Global Contiguous SIF of OCO‐2 (2019)
    Wiley
    Details
    Publication Date: 2019
    Description: Abstract The Orbiting Carbon Observatory‐2 (OCO‐2) collects solar‐induced chlorophyll fluorescence (SIF) at high spatial resolution along orbits ( oco2_orbit), but its discontinuous spatial coverage precludes its full potential for understanding the mechanistic SIF‐photosynthesis relationship. This study developed a spatially contiguous global OCO‐2 SIF product at 0.05° and 16‐day resolutions ( oco2_005) using machine learning constrained by physiological understandings. This was achieved by stratifying biomes and times for training and predictions, which accounts for varying plant physiological properties in space and time. oco2_005 accurately preserved the spatiotemporal variations of oco2_orbit across the globe. Validation of oco2_005 with Chlorophyll Fluorescence Imaging Spectrometer airborne measurements revealed striking consistency (R2 = 0.72; regression slope = 0.96). Further, without time and biome stratification, (1) oco2_005 of croplands, deciduous temperate, and needleleaf forests would be underestimated during the peak season, (2) oco2_005 of needleleaf forests would be overestimated during autumn, and (3) the capability of oco2_005 to detect drought would be diminished.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 9
    facet.materialart.
    Unknown
    Remote Sensing of Chlorophyll Fluorescence in the Ocean Using Imaging Spectrometry: Toward a Vertical Profile of Fluorescence (2019)
    Wiley
    Details
    Publication Date: 2019
    Description: Abstract Chlorophyll fluorescence measurements provide valuable information on phytoplankton abundance and physiology. High spectral resolution measurements from the aircraft‐mounted Portable Remote Imaging SpectroMeter (PRISM) allow for a more robust and informative fluorescence measurement than previous methods. An increase in radiation in the fluorescence wavelength range is approximated by a skew‐normal distribution. Positive skew suggests the influence of water attenuation and motivates the use of an inverse retrieval model to solve for the most likely vertical distribution of fluorescence quantum yield. This approach is tested with theoretical fluorescence profiles and applied to a PRISM flightline located in southern Drake Passage, Southern Ocean during austral summer. The resulting profiles suggest vertical structure in fluorescence quantum yield in the upper 10 m, which matches expectations from in situ studies. The framework developed in this paper can be applied to current and future satellite missions, providing more information on phytoplankton concentrations, vertical profiles, and physiology.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 10
    facet.materialart.
    Unknown
    Assessing methane emissions from global space-borne observations (2005)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2005-03-19
    Description: In the past two centuries, atmospheric methane has more than doubled and now constitutes 20% of the anthropogenic climate forcing by greenhouse gases. Yet its sources are not well quantified, introducing uncertainties in its global budget. We retrieved the global methane distribution by using spaceborne near-infrared absorption spectroscopy. In addition to the expected latitudinal gradient, we detected large-scale patterns of anthropogenic and natural methane emissions. Furthermore, we observed unexpectedly high methane concentrations over tropical rainforests, revealing that emission inventories considerably underestimated methane sources in these regions during the time period of investigation (August through November 2003).〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Frankenberg, C -- Meirink, J F -- van Weele, M -- Platt, U -- Wagner, T -- New York, N.Y. -- Science. 2005 May 13;308(5724):1010-4. Epub 2005 Mar 17.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute of Environmental Physics, University of Heidelberg, INF 229, 69120 Heidelberg, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/15774724" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...