Evaluation of fraction of absorbed photosynthetically active radiation products for different canopy radiation transfer regimes: Methodology and results using Joint Research Center products derived from SeaWiFS against ground‐based estimations

Gobron, Nadine; Pinty, B.; Aussedat, Ophélie; Chen, Jing M.; Cohen, Warren B.; Fensholt, Rasmus; Gond, Valéry; Huemmrich, K. F.; Lee, Thomas; Mélin, Frédéric; Privette, Jeffrey L.; Sandholt, Inge; Taberner, Malcolm; Turner, David P.; Verstraete, M. M.; Widlowski, Jean-Luc

doi:10.1029/2005jd006511

Cited by 157 publications

(153 citation statements)

References 43 publications

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“…The linear relationship is supposed to level off towards higher values of LAI (≥4.5; Gobron et al, 2006), which were not reached in this study.…”

Section: Discussionmentioning

confidence: 85%

“…(n=11) variability in the global terrestrial cycles of water and carbon (Williams et al, 2007;Weber et al, 2009). Moreover, all African ecosystems will likely experience increasing climate-change-driven and human pressure in the future (Fuller and Prince, 1996;Williams et al, 2007). Improved quantification of the atmospheric carbon exchange across vegetation types thus provides fundamental information that can, for instance, be used to evaluate the performance of current terrestrial carbon cycle models.…”

Section: Discussionmentioning

confidence: 99%

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Precipitation as driver of carbon fluxes in 11 African ecosystems

et al. 2009

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Abstract. This study reports carbon and water fluxes between the land surface and atmosphere in eleven different ecosystems types in Sub-Saharan Africa, as measured using eddy covariance (EC) technology in the first two years of the CarboAfrica network operation. The ecosystems for which data were available ranged in mean annual rainfall from 320 mm (Sudan) to 1150 mm (Republic of Congo) and include a spectrum of vegetation types (or land cover) (open savannas, woodlands, croplands and grasslands). Given the shortness of the record, the EC data were analysed across the network rather than longitudinally at sites, in order to understand the driving factors for ecosystem respiration and carbon assimilation, and to reveal the different water use strategies in these highly seasonal environments.Correspondence to: L. Merbold (lmerbold@bgc-jena.mpg.de) Values for maximum net carbon assimilation rates (photosynthesis) ranged from −12.5 µmol CO 2 m −2 s −1 in a dry, open Millet cropland (C 4 -plants) up to −48 µmol CO 2 m −2 s −1 for a tropical moist grassland. Maximum carbon assimilation rates were highly correlated with mean annual rainfall (r 2 =0.74). Maximum photosynthetic uptake rates (Fp max ) were positively related to satellite-derived f APAR . Ecosystem respiration was dependent on temperature at all sites, and was additionally dependent on soil water content at sites receiving less than 1000 mm of rain per year. All included ecosystems dominated by C 3 -plants, showed a strong decrease in 30-min assimilation rates with increasing water vapour pressure deficit above 2.0 kPa.

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“…The linear relationship is supposed to level off towards higher values of LAI (≥4.5; Gobron et al, 2006), which were not reached in this study.…”

Section: Discussionmentioning

confidence: 85%

Section: Discussionmentioning

confidence: 99%

Precipitation as driver of carbon fluxes in 11 African ecosystems

et al. 2009

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“…This yielded a global data set composed of monthly estimates of local ET and meteorological records from each tower (a total of 4,678 site-months within the period 1997-2006), along with satellite observations of the fraction of photosynthetically active radiation absorbed by the canopy (FAPAR) at 2-km resolution from the sea-viewing wide field-of-view sensor (SeaWiFS; ref. 24), and site-level information on vegetation type and local climate (Supplementary Data Section 1). We used this global data set to train the MTE to create maps of gridded monthly ET at 0.5u resolution covering the whole period 1982-2008.…”

Section: Methods Summarymentioning

confidence: 99%

Recent decline in the global land evapotranspiration trend due to limited moisture supply

Jung

Reichstein

Ciais

et al. 2010

Nature

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1,836

1,462

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More than half of the solar energy absorbed by land surfaces is currently used to evaporate water(1). Climate change is expected to intensify the hydrological cycle(2) and to alter evapotranspiration, with implications for ecosystem services and feedback to regional and global climate. Evapotranspiration changes may already be under way, but direct observational constraints are lacking at the global scale. Until such evidence is available, changes in the water cycle on land-a key diagnostic criterion of the effects of climate change and variability-remain uncertain. Here we provide a data-driven estimate of global land evapotranspiration from 1982 to 2008, compiled using a global monitoring network(3), meteorological and remote-sensing observations, and a machine-learning algorithm(4). In addition, we have assessed evapotranspiration variations over the same time period using an ensemble of process-based land-surface-models. Our results suggest that global annual evapotranspiration increased on average by 7.1 +/- 1.0 millimetres per year per decade from 1982 to 1997. After that, coincident with the last major El Nino event in 1998, the global evapotranspiration increase seems to have ceased until 2008. This change was driven primarily by moisture limitation in the Southern Hemisphere, particularly Africa and Australia. In these regions, microwave satellite observations indicate that soil moisture decreased from 1998 to 2008. Hence, increasing soil-moisture limitations on evapotranspiration largely explain the recent decline of the global land-evapotranspiration trend. Whether the changing behaviour of evapotranspiration is representative of natural climate variability or reflects a more permanent reorganization of the land water cycle is a key question for earth system science

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“…In view of the difficulties in ground measurements, sensors onboard satellite now provide the only available FAPAR estimates from local to global scales [5][6][7], such as moderate-resolution imaging spectroradiometer (MODIS) [8], Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) [9], observations in HiWATER [32]. The study area features a compound of croplands (72%), residential land (24%) and woodland (4%).…”

Section: Introductionmentioning

confidence: 99%

Scaling of FAPAR from the Field to the Satellite

Wang

Xie

Liu³

et al. 2016

Remote Sensing

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Abstract:The fraction of absorbed photosynthetically active radiation (FAPAR) is a critical biophysical parameter in eco-environmental studies. Scaling of FAPAR from the field observation to the satellite pixel is essential for validating remote sensing FAPAR product and for further modeling applications. However, compared to spatial mismatches, few studies have considered temporal mismatches between in-situ and satellite observations in the scaling. This paper proposed a general methodology for scaling FAPAR from the field to the satellite pixel considering the temporal variation. Firstly, a temporal normalization method was proposed to normalize the in-situ data measured at different times to the time of satellite overpass. The method was derived from the integration of an atmospheric radiative transfer model (6S) and a FAPAR analytical model (FAPAR-P), which can characterize the diurnal variations of FAPAR comprehensively. Secondly, the logistic model, which derives smooth and consistent temporal profile for vegetation growth, was used to interpolate the in-situ data to match the dates of satellite acquisitions. Thirdly, fine-resolution FAPAR products at different dates were estimated from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data using the temporally corrected in-situ data. Finally, fine-resolution FAPAR were taken as reference datasets and aggregated to coarse resolution, which were further compared to the Moderate Resolution Imaging Spectroradiometer (MODIS) FAPAR product. The methodology is validated for scaling FAPAR from the field to the satellite pixel temporally and spatially. The MODIS FAPAR manifested a good consistency with the aggregated FAPAR with R 2 of 0.922 and the root mean squared error of 0.054.

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Evaluation of fraction of absorbed photosynthetically active radiation products for different canopy radiation transfer regimes: Methodology and results using Joint Research Center products derived from SeaWiFS against ground‐based estimations

Cited by 157 publications

References 43 publications

Precipitation as driver of carbon fluxes in 11 African ecosystems

Precipitation as driver of carbon fluxes in 11 African ecosystems

Recent decline in the global land evapotranspiration trend due to limited moisture supply

Scaling of FAPAR from the Field to the Satellite

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