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  • 1
    Online Resource
    Online Resource
    Regional inversion of CO〈sub〉2〈/sub〉 ecosystem fluxes from atmospheric measurements: reliability of the uncertainty estimates
    Copernicus GmbH ; 2013
    In:  Atmospheric Chemistry and Physics Vol. 13, No. 17 ( 2013-09-10), p. 9039-9056
    Details
    In: Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 13, No. 17 ( 2013-09-10), p. 9039-9056
    Abstract: Abstract. The Bayesian framework of CO2 flux inversions permits estimates of the retrieved flux uncertainties. Here, the reliability of these theoretical estimates is studied through a comparison against the misfits between the inverted fluxes and independent measurements of the CO2 Net Ecosystem Exchange (NEE) made by the eddy covariance technique at local (few hectares) scale. Regional inversions at 0.5° resolution are applied for the western European domain where ~ 50 eddy covariance sites are operated. These inversions are conducted for the period 2002–2007. They use a mesoscale atmospheric transport model, a prior estimate of the NEE from a terrestrial ecosystem model and rely on the variational assimilation of in situ continuous measurements of CO2 atmospheric mole fractions. Averaged over monthly periods and over the whole domain, the misfits are in good agreement with the theoretical uncertainties for prior and inverted NEE, and pass the chi-square test for the variance at the 30% and 5% significance levels respectively, despite the scale mismatch and the independence between the prior (respectively inverted) NEE and the flux measurements. The theoretical uncertainty reduction for the monthly NEE at the measurement sites is 53% while the inversion decreases the standard deviation of the misfits by 38%. These results build confidence in the NEE estimates at the European/monthly scales and in their theoretical uncertainty from the regional inverse modelling system. However, the uncertainties at the monthly (respectively annual) scale remain larger than the amplitude of the inter-annual variability of monthly (respectively annual) fluxes, so that this study does not engender confidence in the inter-annual variations. The uncertainties at the monthly scale are significantly smaller than the seasonal variations. The seasonal cycle of the inverted fluxes is thus reliable. In particular, the CO2 sink period over the European continent likely ends later than represented by the prior ecosystem model.
    Type of Medium: Online Resource
    ISSN: 1680-7324
    URL: Article
    DOI: 10.5194/acp-13-9039-2013
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2013
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  • 2
    Online Resource
    Online Resource
    Current systematic carbon-cycle observations and the need for implementing a policy-relevant carbon observing system
    Copernicus GmbH ; 2014
    In:  Biogeosciences Vol. 11, No. 13 ( 2014-07-03), p. 3547-3602
    Details
    In: Biogeosciences, Copernicus GmbH, Vol. 11, No. 13 ( 2014-07-03), p. 3547-3602
    Abstract: Abstract. A globally integrated carbon observation and analysis system is needed to improve the fundamental understanding of the global carbon cycle, to improve our ability to project future changes, and to verify the effectiveness of policies aiming to reduce greenhouse gas emissions and increase carbon sequestration. Building an integrated carbon observation system requires transformational advances from the existing sparse, exploratory framework towards a dense, robust, and sustained system in all components: anthropogenic emissions, the atmosphere, the ocean, and the terrestrial biosphere. The paper is addressed to scientists, policymakers, and funding agencies who need to have a global picture of the current state of the (diverse) carbon observations. We identify the current state of carbon observations, and the needs and notional requirements for a global integrated carbon observation system that can be built in the next decade. A key conclusion is the substantial expansion of the ground-based observation networks required to reach the high spatial resolution for CO2 and CH4 fluxes, and for carbon stocks for addressing policy-relevant objectives, and attributing flux changes to underlying processes in each region. In order to establish flux and stock diagnostics over areas such as the southern oceans, tropical forests, and the Arctic, in situ observations will have to be complemented with remote-sensing measurements. Remote sensing offers the advantage of dense spatial coverage and frequent revisit. A key challenge is to bring remote-sensing measurements to a level of long-term consistency and accuracy so that they can be efficiently combined in models to reduce uncertainties, in synergy with ground-based data. Bringing tight observational constraints on fossil fuel and land use change emissions will be the biggest challenge for deployment of a policy-relevant integrated carbon observation system. This will require in situ and remotely sensed data at much higher resolution and density than currently achieved for natural fluxes, although over a small land area (cities, industrial sites, power plants), as well as the inclusion of fossil fuel CO2 proxy measurements such as radiocarbon in CO2 and carbon-fuel combustion tracers. Additionally, a policy-relevant carbon monitoring system should also provide mechanisms for reconciling regional top-down (atmosphere-based) and bottom-up (surface-based) flux estimates across the range of spatial and temporal scales relevant to mitigation policies. In addition, uncertainties for each observation data-stream should be assessed. The success of the system will rely on long-term commitments to monitoring, on improved international collaboration to fill gaps in the current observations, on sustained efforts to improve access to the different data streams and make databases interoperable, and on the calibration of each component of the system to agreed-upon international scales.
    Type of Medium: Online Resource
    ISSN: 1726-4189
    URL: Article
    DOI: 10.5194/bg-11-3547-2014
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2014
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  • 3
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    Online Resource
    An attempt at estimating Paris area CO〈sub〉2〈/sub〉 emissions from atmospheric concentration measurements
    Copernicus GmbH ; 2015
    In:  Atmospheric Chemistry and Physics Vol. 15, No. 4 ( 2015-02-18), p. 1707-1724
    Details
    In: Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 15, No. 4 ( 2015-02-18), p. 1707-1724
    Abstract: Abstract. Atmospheric concentration measurements are used to adjust the daily to monthly budget of fossil fuel CO2 emissions of the Paris urban area from the prior estimates established by the Airparif local air quality agency. Five atmospheric monitoring sites are available, including one at the top of the Eiffel Tower. The atmospheric inversion is based on a Bayesian approach, and relies on an atmospheric transport model with a spatial resolution of 2 km with boundary conditions from a global coarse grid transport model. The inversion adjusts prior knowledge about the anthropogenic and biogenic CO2 fluxes from the Airparif inventory and an ecosystem model, respectively, with corrections at a temporal resolution of 6 h, while keeping the spatial distribution from the emission inventory. These corrections are based on assumptions regarding the temporal autocorrelation of prior emissions uncertainties within the daily cycle, and from day to day. The comparison of the measurements against the atmospheric transport simulation driven by the a priori CO2 surface fluxes shows significant differences upwind of the Paris urban area, which suggests a large and uncertain contribution from distant sources and sinks to the CO2 concentration variability. This contribution advocates that the inversion should aim at minimising model–data misfits in upwind–downwind gradients rather than misfits in mole fractions at individual sites. Another conclusion of the direct model–measurement comparison is that the CO2 variability at the top of the Eiffel Tower is large and poorly represented by the model for most wind speeds and directions. The model's inability to reproduce the CO2 variability at the heart of the city makes such measurements ill-suited for the inversion. This and the need to constrain the budgets for the whole city suggests the assimilation of upwind–downwind mole fraction gradients between sites at the edge of the urban area only. The inversion significantly improves the agreement between measured and modelled concentration gradients. Realistic emissions are retrieved for two 30-day periods and suggest a significant overestimate by the AirParif inventory. Similar inversions over longer periods are necessary for a proper evaluation of the optimised CO2 emissions against independent data.
    Type of Medium: Online Resource
    ISSN: 1680-7324
    URL: Article
    URL: Article
    DOI: 10.5194/acp-15-1707-2015
    DOI: 10.5194/acp-15-1707-2015-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2015
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  • 4
    Online Resource
    Online Resource
    Remote sensing of aerosols over land surfaces from POLDER‐ADEOS‐1 polarized measurements
    American Geophysical Union (AGU) ; 2001
    In:  Journal of Geophysical Research: Atmospheres Vol. 106, No. D5 ( 2001-03-16), p. 4913-4926
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 106, No. D5 ( 2001-03-16), p. 4913-4926
    Abstract: The polarization measurements achieved by the POLDER instrument on ADEOS‐1 are used for the remote sensing of aerosols over land surfaces. The key advantage of using polarized observations is their ability to systematically correct for the ground contribution, whereas the classical approach using natural light fails. The estimation of land surface polarizing properties from POLDER has been examined in a previous paper. Here we consider how the optical thickness δ 0 and Ångstrom exponent α of aerosols are derived from the polarized light backscattered by the particles. The inversion scheme is detailed, and illustrative results are presented. Maps of the retrieved optical thickness allow for detection of large aerosol features, and in the case of small aerosols, the δ 0 and α retrievals are consistent with correlative ground‐based measurements. However, because polarized light stems mainly from small particles, the results are biased for aerosol distributions containing coarser modes of particles. To overcome this limitation, an aerosol index defined as the product AI = δ 0 α is proposed. Theoretical analysis and comparison with ground‐based measurements suggest that AI is approximately the same when using δ 0 , and α is related to the entire aerosol size distribution or derived from the polarized light originating from the small polarizing particles alone. This invariance is specially assessed by testing the continuity of AI across coastlines, given the unbiased properties of aerosol retrieval over ocean. Although reducing the information concerning the aerosols, this single parameter allows a link between the POLDER aerosol surveys over land and ocean. POLDER aerosol index global maps enable the monitoring of major aerosol sources over continental areas.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/2000JD900364
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2001
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    detail.hit.zdb_id: 3094268-8
    detail.hit.zdb_id: 710256-2
    detail.hit.zdb_id: 2016804-4
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    detail.hit.zdb_id: 3094219-6
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    SSG: 16,13
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  • 5
    Online Resource
    Online Resource
    Remote sensing of aerosols by using polarized, directional and spectral measurements within the A-Train: the PARASOL mission
    Copernicus GmbH ; 2011
    In:  Atmospheric Measurement Techniques Vol. 4, No. 7 ( 2011-07-12), p. 1383-1395
    Details
    In: Atmospheric Measurement Techniques, Copernicus GmbH, Vol. 4, No. 7 ( 2011-07-12), p. 1383-1395
    Abstract: Abstract. Instruments dedicated to aerosol monitoring are recently available and the POLDER (POLarization and Directionality of the Earth's Reflectances) instrument on board the PARASOL (Polarization & Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a Lidar) mission is one of them. By measuring the spectral, angular and polarization properties of the radiance at the top of the atmosphere, in coordination with the other A-Train instruments, PARASOL provides the aerosol optical depths (AOD) as well as several optical and microphysical aerosol properties. The instrument, the inversion schemes and the list of aerosol parameters are described. Examples of retrieved aerosol parameters are provided as well as innovative approaches and further inversion techniques.
    Type of Medium: Online Resource
    ISSN: 1867-8548
    URL: Article
    DOI: 10.5194/amt-4-1383-2011
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2011
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  • 6
    Online Resource
    Online Resource
    Evaluation of a Global Vegetation Model using time series of satellite vegetation indices
    Copernicus GmbH ; 2011
    In:  Geoscientific Model Development Vol. 4, No. 4 ( 2011-12-05), p. 1103-1114
    Details
    In: Geoscientific Model Development, Copernicus GmbH, Vol. 4, No. 4 ( 2011-12-05), p. 1103-1114
    Abstract: Abstract. Atmospheric CO2 drives most of the greenhouse effect increase. One major uncertainty on the future rate of increase of CO2 in the atmosphere is the impact of the anticipated climate change on the vegetation. Dynamic Global Vegetation Models (DGVM) are used to address this question. ORCHIDEE is such a DGVM that has proven useful for climate change studies. However, there is no objective and methodological way to accurately assess each new available version on the global scale. In this paper, we submit a methodological evaluation of ORCHIDEE by correlating satellite-derived Vegetation Index time series against those of the modeled Fraction of absorbed Photosynthetically Active Radiation (FPAR). A perfect correlation between the two is not expected, however an improvement of the model should lead to an increase of the overall performance. We detail two case studies in which model improvements are demonstrated, using our methodology. In the first one, a new phenology version in ORCHIDEE is shown to bring a significant impact on the simulated annual cycles, in particular for C3 Grasses and C3 Crops. In the second case study, we compare the simulations when using two different weather fields to drive ORCHIDEE. The ERA-Interim forcing leads to a better description of the FPAR interannual anomalies than the simulation forced by a mixed CRU-NCEP dataset. This work shows that long time series of satellite observations, despite their uncertainties, can identify weaknesses in global vegetation models, a necessary first step to improving them.
    Type of Medium: Online Resource
    ISSN: 1991-9603
    URL: Article
    URL: Article
    DOI: 10.5194/gmd-4-1103-2011
    DOI: 10.5194/gmd-4-1103-2011-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2011
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  • 7
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    First observation of the hot spot from space at sub-degree angular resolution using POLDER data
    Informa UK Limited ; 2003
    In:  International Journal of Remote Sensing Vol. 24, No. 5 ( 2003-01), p. 1103-1110
    Details
    In: International Journal of Remote Sensing, Informa UK Limited, Vol. 24, No. 5 ( 2003-01), p. 1103-1110
    Type of Medium: Online Resource
    ISSN: 0143-1161 , 1366-5901
    URL: Article
    DOI: 10.1080/0143116021000020153
    Language: English
    Publisher: Informa UK Limited
    Publication Date: 2003
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    SSG: 14
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  • 8
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    Assimilation of POLDER aerosol optical thickness into the LMDz-INCA model: Implications for the Arctic aerosol burden
    American Geophysical Union (AGU) ; 2007
    In:  Journal of Geophysical Research Vol. 112, No. D2 ( 2007-01-31)
    Details
    In: Journal of Geophysical Research, American Geophysical Union (AGU), Vol. 112, No. D2 ( 2007-01-31)
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/2005JD006954
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2007
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    SSG: 16,13
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  • 9
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    Vulnerabilities and resilience of European power generation to 1.5 °C, 2 °C and 3 °C warming
    IOP Publishing ; 2018
    In:  Environmental Research Letters Vol. 13, No. 4 ( 2018-04-01), p. 044024-
    Details
    In: Environmental Research Letters, IOP Publishing, Vol. 13, No. 4 ( 2018-04-01), p. 044024-
    Type of Medium: Online Resource
    ISSN: 1748-9326
    URL: Article
    DOI: 10.1088/1748-9326/aab211
    Language: Unknown
    Publisher: IOP Publishing
    Publication Date: 2018
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  • 10
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    Biofuel burning and human respiration bias on satellite estimates of fossil fuel CO 2 emissions
    IOP Publishing ; 2020
    In:  Environmental Research Letters Vol. 15, No. 7 ( 2020-07-01), p. 074036-
    Details
    In: Environmental Research Letters, IOP Publishing, Vol. 15, No. 7 ( 2020-07-01), p. 074036-
    Abstract: The satellites that have been designed to support the monitoring of fossil fuel CO 2 emissions aim to systematically measure atmospheric CO 2 plumes generated by intense emissions from large cities, power plants and industrial sites. These data can be assimilated into atmospheric transport models in order to estimate the corresponding emissions. However, plumes emitted by cities and powerplants contain not only fossil fuel CO 2 but also significant amounts of CO 2 released by human respiration and by the burning of biofuels. We show that these amounts represent a significant proportion of the fossil fuel CO 2 emissions, up to 40% for instance in cities of Nordic countries, and will thus leave some ambiguity in the retrieval of fossil fuel CO 2 emissions from satellite concentration observations. Auxiliary information such as biofuel use statistics and radiocarbon measurement could help reduce the ambiguity and improve the framework of monitoring fossil fuel CO 2 emissions from space.
    Type of Medium: Online Resource
    ISSN: 1748-9326
    URL: Article
    DOI: 10.1088/1748-9326/ab7835
    Language: Unknown
    Publisher: IOP Publishing
    Publication Date: 2020
    detail.hit.zdb_id: 2255379-4
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