Dual-season mapping of wetland inundation and vegetation for the central Amazon basin
TL;DR: In this article, the authors used L-band synthetic aperture radar (SAR) imagery acquired by the Japanese Earth Resources Satellite-1 to map the central Amazon region and produce the first high-resolution wetlands map for the region.
About: This article is published in Remote Sensing of Environment.The article was published on 2003-11-15. It has received 541 citations till now. The article focuses on the topics: Wetland & Thematic map.
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TL;DR: In this paper, it was shown that carbon dioxide discharged to the oceans is only a fraction of that entering rivers from terrestrial ecosystems via soil respiration, leaching, chemical weathering, and physical erosion.
Abstract: Streams, rivers, lakes, and other inland waters are important agents in the coupling of biogeochemical cycles between continents, atmosphere, and oceans. The depiction of these roles in global-scale assessments of carbon (C) and other bioactive elements remains limited, yet recent findings suggest that C discharged to the oceans is only a fraction of that entering rivers from terrestrial ecosystems via soil respiration, leaching, chemical weathering, and physical erosion. Most of this C influx is returned to the atmosphere from inland waters as carbon dioxide (CO2) or buried in sedimentary deposits within impoundments, lakes, floodplains, and other wetlands. Carbon and mineral cycles are coupled by both erosion–deposition processes and chemical weathering, with the latter producing dissolved inorganic C and carbonate buffering capacity that strongly modulate downstream pH, biological production of calcium-carbonate shells, and CO2 outgassing in rivers, estuaries, and coastal zones. Human activities substantially affect all of these processes.
978 citations
TL;DR: The Water and Terrestrial Elevation Recovery mission (WER) as discussed by the authors is a satellite-based approach to estimate the elevation of the water surface (h), its slope (∂h/∂x), and its temporal change.
Abstract: [1] Surface fresh water is essential for life, yet we have surprisingly poor knowledge of the spatial and temporal dynamics of surface freshwater discharge and changes in storage globally. For example, we are unable to answer such basic questions as “What is the spatial and temporal variability of water stored on and near the surface of all continents?” Furthermore, key societal issues, such as the susceptibility of life to flood hazards, cannot be answered with the current global, in situ networks designed to observe river discharge at points but not flood events. The measurements required to answer these hydrologic questions are surface water area, the elevation of the water surface (h), its slope (∂h/∂x), and temporal change (∂h/∂t). Advances in remote sensing hydrology, particularly over the past 10 years and even more recently, have demonstrated that these hydraulic variables can be measured reliably from orbiting platforms. Measurements of inundated area have been used to varying degrees of accuracy as proxies for discharge but are successful only when in situ data are available for calibration; they fail to indicate the dynamic topography of water surfaces. Radar altimeters have a rich, multidecadal history of successfully measuring elevations of the ocean surface and are now also accepted as capable tools for measuring h along orbital profiles crossing freshwater bodies. However, altimeters are profiling tools, which, because of their orbital spacings, miss too many freshwater bodies to be useful hydrologically. High spatial resolution images of ∂h/∂t have been observed with interferometric synthetic aperture radar, but the method requires emergent vegetation to scatter radar pulses back to the receiving antenna. Essentially, existing spaceborne methods have been used to measure components of surface water hydraulics, but none of the technologies can singularly supply the water volume and hydraulic measurements that are needed to accurately model the water cycle and to guide water management practices. Instead, a combined imaging and elevation-measuring approach is ideal as demonstrated by the Shuttle Radar Topography Mission (SRTM), which collected images of h at a high spatial resolution (∼90 m) thus permitting the calculation of ∂h/∂x. We suggest that a future satellite concept, the Water and Terrestrial Elevation Recovery mission, will improve upon the SRTM design to permit multitemporal mappings of h across the world's wetlands, floodplains, lakes, reservoirs, and rivers.
807 citations
Princeton University1, Utrecht University2, Goethe University Frankfurt3, University of California, Irvine4, National Center for Atmospheric Research5, Delft University of Technology6, George Mason University7, University of Bonn8, McGill University9, University of Washington10, Goddard Space Flight Center11, University of Illinois at Urbana–Champaign12, University of Reading13, University of Oxford14
TL;DR: In this article, the authors discuss the needs and benefits for a system that would monitor and predict the Earth's terrestrial water, energy, and biogeochemical cycles, and they call upon the international hydrologic community and the hydrological science support infrastructure to endorse the effort.
Abstract: Monitoring Earth's terrestrial water conditions is critically important to many hydrological applications such as global food production; assessing water resources sustainability; and flood, drought, and climate change prediction. These needs have motivated the development of pilot monitoring and prediction systems for terrestrial hydrologic and vegetative states, but to date only at the rather coarse spatial resolutions (∼10–100 km) over continental to global domains. Adequately addressing critical water cycle science questions and applications requires systems that are implemented globally at much higher resolutions, on the order of 1 km, resolutions referred to as hyperresolution in the context of global land surface models. This opinion paper sets forth the needs and benefits for a system that would monitor and predict the Earth's terrestrial water, energy, and biogeochemical cycles. We discuss six major challenges in developing a system: improved representation of surface-subsurface interactions due to fine-scale topography and vegetation; improved representation of land-atmospheric interactions and resulting spatial information on soil moisture and evapotranspiration; inclusion of water quality as part of the biogeochemical cycle; representation of human impacts from water management; utilizing massively parallel computer systems and recent computational advances in solving hyperresolution models that will have up to 109 unknowns; and developing the required in situ and remote sensing global data sets. We deem the development of a global hyperresolution model for monitoring the terrestrial water, energy, and biogeochemical cycles a “grand challenge” to the community, and we call upon the international hydrologic community and the hydrological science support infrastructure to endorse the effort.
704 citations
TL;DR: In this article, a P-band polarimetric SAR with interferometric capability is used to measure the magnitude and distribution of forest biomass globally to improve resource assessment, carbon accounting and carbon models, and to monitor and quantify changes in terrestrial forest biomass.
592 citations
Cites methods from "Dual-season mapping of wetland inun..."
...The ability of long wavelength radar to map wetland inundation (for example, the Amazon and the Congo basins) has been demonstrated using JERS L-band data (Hess et al., 2003, Martinez and Le Toan, 2007)....
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TL;DR: In this article, a new global river routing model, CaMa-Flood, is proposed, which explicitly parameterizes the subgrid-scale topography of a floodplain, thus describing floodplain inundation dynamics.
Abstract: [1] Current global river routing models do not represent floodplain inundation dynamics realistically because the storage and movement of surface waters are regulated by small-scale topography rather than the commonly used spatial resolution of global models. In this study, we propose a new global river routing model, CaMa-Flood, which explicitly parameterizes the subgrid-scale topography of a floodplain, thus describing floodplain inundation dynamics. The relationship between water storage, water level, and flooded area in the model is decided on the basis of the subgrid-scale topographic parameters based on 1 km resolution digital elevation model. Horizontal water transport is calculated with a diffusive wave equation, which realizes the backwater effect in flat river basins. A set of global-scale river flow simulations demonstrated an improved predictability of daily-scale river discharge in many major world rivers by incorporating the floodplain inundation dynamics. Detailed analysis of the simulated results for the Amazon River suggested that introduction of the diffusive wave equation is essential for simulating water surface elevation realistically. The simulated spatiotemporal variation of the flooded area in the Amazon basin showed a good correlation with satellite observations, especially when the backwater effect was considered. The improved predictability for daily river discharge, water surface elevation, and inundated areas by the proposed model will promote climate system studies and water resource assessments.
498 citations
Cites background or methods from "Dual-season mapping of wetland inun..."
...Figure 8a represents the observed flooded area using SAR‐derived data sets [Hess et al., 2003], whereas 9 of 21 Figures 8b and 8c represent a simulated flooded area by FLD+Diff and FLD+Kine, respectively....
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...Flooded area fraction in the Amazon River basin for (top) September‐October 1995 and (bottom) May‐June 1996: (a) satellite observation [Hess et al., 2003], (b) FLD+Diff, and (c) FLD+Kine....
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...Figure 8a represents the observed flooded area using SAR‐derived data sets [Hess et al., 2003], whereas Figure 6....
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...When the simulated flooded area was compared to the more accurate estimation by SAR imaging [Hess et al., 2003] (the pluses in Figure 9), the amplitudes of seasonal flooding became similar between simulation and observation....
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References
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17 Sep 1998
TL;DR: This chapter discusses Accuracy Assessment, which examines the impact of sample design on cost, statistical Validity, and measuring Variability in the context of data collection and analysis.
Abstract: Introduction Why Accuracy Assessment? Overview Historical Review Aerial Photography Digital Assessments Data Collection Considerations Classification Scheme Statistical Considerations Data Distribution Randomness Spatial Autocorrelation Sample Size Sampling Scheme Sample Unit Reference Data Collection Basic Collection Forms Basic Analysis Techniques Non-Site Specific Assessments Site Specific Assessments Area Estimation/Correction Practicals Impact of Sample Design on Cost Recommendations for Collecting Reference Data ASources of Variation in Reference Data Photo Interpretation vs. Ground Visitation Interpreter Variability Observations vs. Measurements What is Correct? Labeling Map vs. Labeling the Reference Data Qualitative vs. Quantitative Analysis Local vs. Regional vs. Global Assessments Advanced Topics Beyond the Error Matrix Modifying the Error Matrix Fuzzy Set Theory Measuring Variability Complex Data Sets Change Detection Multi-Layer Assessments California Hardwood Rangeland Monitoring Project Case Study Balancing Statistical Validity with Practical Reality Bibliography
4,586 citations
"Dual-season mapping of wetland inun..." refers background or methods in this paper
...Following the formulation of Congalton and Green (1999), for a given number of classes k, desired precision b, and desired confidence level 1 a, the required sample size n is given by n ¼ BPð1 PÞ=b2; ð1Þ where B is equal to the upper (a/k) 100th percentile of the v2 distribution with 1 degree of…...
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...(1) thus simplifies to n =B/4b2 (Congalton & Green, 1999)....
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...Following the formulation of Congalton and Green (1999), for a given number of classes k, desired precision b, and desired confidence level 1 a, the required sample size n is given by...
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TL;DR: The IGBP DISCover global land cover product as mentioned in this paper is an integral component of the Global Land Cover database, which provides a unique view of the broad patterns of the biogeographical and ecoclimatic diversity of the global land surface and presents a detailed interpretation of the extent of human development.
Abstract: Researchers from the U.S. Geological Survey, University of Nebraska-Lincoln and the European Commission's Joint Research Centre, Ispra, Italy produced a 1 km resolution global land cover characteristics database for use in a wide range of continental-to global-scale environmental studies. This database provides a unique view of the broad patterns of the biogeographical and ecoclimatic diversity of the global land surface, and presents a detailed interpretation of the extent of human development. The project was carried out as an International Geosphere-Biosphere Programme, Data and Information Systems (IGBP-DIS) initiative. The IGBP DISCover global land cover product is an integral component of the global land cover database. DISCover includes 17 general land cover classes defined to meet the needs of IGBP core science projects. A formal accuracy assessment of the DISCover data layer will be completed in 1998. The 1 km global land cover database was developed through a continent-by-continent unsupervised ...
2,365 citations
"Dual-season mapping of wetland inun..." refers background in this paper
...Global or continental maps of land cover derived from coarse-resolution optical data have emphasized nonwetland cover: they have either omitted wetlands as a class (Hansen, Fries, Townshend, & Sohlberg, 2000; Stone, Schlesinger, Houghton, & Woodwell, 1994) or have significantly underestimated wetland area (Loveland et al., 2000)....
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...…cover derived from coarse-resolution optical data have emphasized nonwetland cover: they have either omitted wetlands as a class (Hansen, Fries, Townshend, & Sohlberg, 2000; Stone, Schlesinger, Houghton, & Woodwell, 1994) or have significantly underestimated wetland area (Loveland et al., 2000)....
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TL;DR: In this paper, a 1km spatial resolution land cover classification using data for 1992-1993 from the Advanced Very High Resolution Radiometer (AVHRR) is presented. But the approach taken involved a hierarchy of pair-wise class trees where a logic based on vegetation form was applied until all classes were depicted.
Abstract: This paper on reports the production of a 1km spatial resolution land cover classie cation using data for 1992- 1993 from the Advanced Very High Resolution Radiometer (AVHRR). This map will be included as an at-launch product of the Moderate Resolution Imaging Spectroradiometer (MODIS) to serve as an input for several algorithms requiring knowledge of land cover type. The methodology was derived from a similar e A ort to create a product at 8km spatial resolution, where high resolution data sets were interpreted in order to derive a coarse-resolution training data set. A set of 37294 O 1km pixels was used within a hierarchical tree structure to classify the AVHRR data into 12 classes. The approach taken involved a hierarchy of pair-wise class trees where a logic based on vegetation form was applied until all classes were depicted. Multi- temporal AVHRR metrics were used to predict class memberships. Minimum annual red ree ectance, peak annual Normalized Di A erence Vegetation Index (NDVI), and minimum channel three brightness temperature were among the most used metrics. Depictions of forests and woodlands, and areas of mechanized agriculture are in general agreement with other sources of information, while classes such as low biomass agriculture and high-latitude broadleaf forest are not. Comparisons of the e nal product with regional digital land cover maps derived from high-resolution remotely sensed data reveal general agreement, except for apparently poor depictions of temperate pastures within areas of agriculture. Distinguishing between forest and non-forest was achieved with agreements ran- ging from 81 to 92% for these regional subsets. The agreements for all classes varied from an average of 65% when viewing all pixels to an average of 82% when viewing only those 1km pixels consisting of greater than 90% one class within the high-resolution data sets.
2,188 citations
TL;DR: It is suggested that the overall carbon budget of rainforests, summed across terrestrial and aquatic environments, appears closer to being in balance than would be inferred from studies of uplands alone.
Abstract: Terrestrial ecosystems in the humid tropics play a potentially important but presently ambiguous role in the global carbon cycle. Whereas global estimates of atmospheric CO2 exchange indicate that the tropics are near equilibrium or are a source with respect to carbon, ground-based estimates indicate that the amount of carbon that is being absorbed by mature rainforests is similar to or greater than that being released by tropical deforestation (about 1.6 Gt C yr-1). Estimates of the magnitude of carbon sequestration are uncertain, however, depending on whether they are derived from measurements of gas fluxes above forests or of biomass accumulation in vegetation and soils. It is also possible that methodological errors may overestimate rates of carbon uptake or that other loss processes have yet to be identified. Here we demonstrate that outgassing (evasion) of CO2 from rivers and wetlands of the central Amazon basin constitutes an important carbon loss process, equal to 1.2 +/- 0.3 Mg C ha-1 yr-1. This carbon probably originates from organic matter transported from upland and flooded forests, which is then respired and outgassed downstream. Extrapolated across the entire basin, this flux-at 0.5 Gt C yr-1-is an order of magnitude greater than fluvial export of organic carbon to the ocean. From these findings, we suggest that the overall carbon budget of rainforests, summed across terrestrial and aquatic environments, appears closer to being in balance than would be inferred from studies of uplands alone.
1,010 citations
"Dual-season mapping of wetland inun..." refers methods in this paper
...The suitability of the classification approach used in this study for regional biogeochemical modeling was demonstrated by Richey et al. (2002)....
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TL;DR: The design and implementation of SPRING is discussed, a geographical information system designed to support environmental projects over large spatial data base, based on an object-oriented data model that caters for the diversity of data sources and formats.
868 citations