The utility of remotely sensed CO2 concentration data in surface source inversions
TL;DR: In this article, the authors used synthesis inversion to compare the uncertainties in regional sources calculated from a moderate-sized surface network and either global or oceanic coverage of column-integrated pseudodata.
Abstract: This paper aims to establish the required precision for column-integrated CO2 concentration data to be useful in constraining surface sources. We use the method of synthesis inversion and compare the uncertainties in regional sources calculated from a moderate-sized surface network and either global or oceanic coverage of column-integrated pseudodata. With a simple measure of total uncertainty, we require precision of monthly averaged column data better than 2.5 ppmv on a 8° × 10° footprint for comparable performance with the existing surface network. If coverage is only oceanic we require 1.5 ppmv precision. We recommend more detailed studies on the feasibility of obtaining such observations from current and future satellite instruments.
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TL;DR: An estimate of net CO2 exchange between the terrestrial biosphere and the atmosphere across North America for every week in the period 2000 through 2005 is presented, derived from a set of 28,000 CO2 mole fraction observations in the global atmosphere that are fed into a state-of-the-art data assimilation system for CO2 called CarbonTracker.
Abstract: We present an estimate of net CO2 exchange between the terrestrial biosphere and the atmosphere across North America for every week in the period 2000 through 2005. This estimate is derived from a set of 28,000 CO2 mole fraction observations in the global atmosphere that are fed into a state-of-the-art data assimilation system for CO2 called CarbonTracker. By design, the surface fluxes produced in CarbonTracker are consistent with the recent history of CO2 in the atmosphere and provide constraints on the net carbon flux independent from national inventories derived from accounting efforts. We find the North American terrestrial biosphere to have absorbed −0.65 PgC/yr (1 petagram = 1015 g; negative signs are used for carbon sinks) averaged over the period studied, partly offsetting the estimated 1.85 PgC/yr release by fossil fuel burning and cement manufacturing. Uncertainty on this estimate is derived from a set of sensitivity experiments and places the sink within a range of −0.4 to −1.0 PgC/yr. The estimated sink is located mainly in the deciduous forests along the East Coast (32%) and the boreal coniferous forests (22%). Terrestrial uptake fell to −0.32 PgC/yr during the large-scale drought of 2002, suggesting sensitivity of the contemporary carbon sinks to climate extremes. CarbonTracker results are in excellent agreement with a wide collection of carbon inventories that form the basis of the first North American State of the Carbon Cycle Report (SOCCR), to be released in 2007. All CarbonTracker results are freely available at http://carbontracker.noaa.gov.
898 citations
TL;DR: The TCCON provides a link between satellite measurements and the extensive ground-based in situ network and achieves an accuracy and precision in total column measurements that is unprecedented for remote-sensing observations.
Abstract: A global network of ground-based Fourier transform spectrometers has been founded to remotely measure column abundances of CO_2, CO, CH_4, N_(2)O and other molecules that absorb in the near-infrared. These measurements are directly comparable with the near-infrared total column measurements from space-based instruments. With stringent requirements on the instrumentation, acquisition procedures, data processing and calibration, the Total Carbon Column Observing Network (TCCON) achieves an
accuracy and precision in total column measurements that is unprecedented for remotesensing observations (better than 0.25% for CO_2). This has enabled carbon-cycle science
investigations using the TCCON dataset, and allows the TCCON to provide a link between satellite measurements and the extensive ground-based in situ network.
768 citations
TL;DR: The Greenhouse Gases Observing Satellite (GOSAT) monitors carbon dioxide and methane globally from space using two instruments using an ultraviolet (UV), visible, near infrared, and SWIR radiometer.
Abstract: The Greenhouse Gases Observing Satellite (GOSAT) monitors carbon dioxide (CO2) and methane (CH4) globally from space using two instruments. The Thermal and Near Infrared Sensor for Carbon Observation Fourier-Transform Spectrometer (TANSO-FTS) detects gas absorption spectra of the solar short wave infrared (SWIR) reflected on the Earth's surface as well as of the thermal infrared radiated from the ground and the atmosphere. TANSO-FTS is capable of detecting three narrow bands (0.76, 1.6, and 2.0 μm) and a wide band (5.5-14.3 μm) with 0.2 cm−1 spectral resolution (interval). The TANSO Cloud and Aerosol Imager (TANSO-CAI) is an ultraviolet (UV), visible, near infrared, and SWIR radiometer designed to detect cloud and aerosol interference and to provide the data for their correction. GOSAT is placed in a sun-synchronous orbit 666 km at 13:00 local time, with an inclination angle of 98 °. A brief overview of the GOSAT project, scientific requirements, instrument designs, hardware performance, on-orbit operation, and data processing is provided.
734 citations
California Institute of Technology1, Goddard Space Flight Center2, University of Bremen3, National Institute of Water and Atmospheric Research4, Woods Hole Oceanographic Institution5, University of California, Berkeley6, Harvard University7, Haverford College8, Commonwealth Scientific and Industrial Research Organisation9, Colorado State University10, Climate Monitoring and Diagnostics Laboratory11, Goodrich Corporation12
TL;DR: The Orbiting Carbon Observatory (OCO) as mentioned in this paper is the first global, space-based measurements of atmospheric carbon dioxide (CO 2 ) with the precision, resolution and coverage needed to characterize CO 2 sources and sinks on regional scales.
539 citations
30 May 2006
TL;DR: The authors collected the first space-based measurements of atmospheric CO2 with the precision, resolution, and coverage needed to characterize its sources and sinks on regional scales and quantify their variability over the seasonal cycle.
Abstract: Science objectives include: Collect the first space-based measurements of atmospheric CO2 with the precision, resolution, and coverage needed to characterize its sources and sinks on regional scales and quantify their variability over the seasonal cycle. Use independent data validation approaches to ensure high accuracy (1-2 ppm, 0.3% - 0.5%). Reliable climate predictions require an improved understanding of CO2 sinks. What human and natural processes are controlling atmospheric CO2? What are the relative roles of the oceans and land ecosystems in absorbing CO2?
524 citations
Cites background from "The utility of remotely sensed CO2 ..."
...Modeling studies with source-sink inversion models [1] indicate that our understanding of CO2 sources and sinks could be improved substantially if data from the existing ground-based CO2 monitoring network were augmented by global, space-based measurements of the columnintegrated CO2 dry air mole fraction (XCO2) with accuracies of ~0....
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References
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TL;DR: In this article, the authors recover the space-time structure of fluxes of CO 2 to the atmosphere over the period 1980-1995 from atmospheric concentration and isotopic composition measurements using Bayesian synthesis inversion in which sources are aggregated into large regions and their strengths adjusted to match observed concentrations.
Abstract: This paper presents an attempt to recover the space–time structure of fluxes of CO 2 to the atmosphere over the period 1980–1995 from atmospheric concentration and isotopic composition measurements. The technique used is Bayesian synthesis inversion in which sources are aggregated into large regions and their strengths adjusted to match observed concentrations. The sources are constrained by prior estimates based on a priori knowledge. The input data are atmospheric CO 2 concentration measurements from the NOAA/CMDL network, 13 CO 2 composition and O2/N2 ratios measured at Cape Grim, Tasmania by CSIRO Atmospheric Research. The primary findings are a relatively large long-term mean ocean uptake of CO 2 , and seasonal fluxes over land with similar integrated magnitude, but smaller peak amplitude, compared with those derived by Fung and co-workers. Predicted interannual variability is smaller than reported in previous studies. The largest contributor is the oceanic tropics where fluxes vary on the time scale of the southern oscillation. There is evidence of longer time-scale variation in land uptake. Increases in ocean uptake and northern land uptake in the early 1990s are consistent with a response to the Mt. Pinatubo eruption. DOI: 10.1034/j.1600-0889.1999.t01-1-00008.x
420 citations
"The utility of remotely sensed CO2 ..." refers methods in this paper
...The method we use is Bayesian synthesis inversion previously used for atmospheric trace gas studies by Enting et al. (1995) and Rayner et al. (1999)....
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...In both of these we follow Rayner et al. (1999)....
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TL;DR: In this article, a synthesis inversion technique is used to estimate CO 2 fluxes to and from the atmosphere, and the authors find that within the range of ≈ 1.2 Gt C y -1 their unconstrained estimates of air-sea flux are very sensitive to the choice of data that are fitted.
Abstract: A synthesis inversion technique is used to estimate CO 2 fluxes to and from the atmosphere. Concentrations calculated by the GISS atmospheric tracer transport model are fitted to observations of CO 2 and 13 CO 2 . The procedure uses the uncertainty in the data to derive measures of uncertainty for the estimated sources, thus allowing a comparison of the relative importance of various data items in reducing these uncertainties. We analysed two periods. The first, 1986-1987, was intended to be representative of these and earlier years. The CO 2 data appear generally representative but the inversion produces some features that may reflect El Nino conditions. The second period was 1989-1990 which had anomalous behaviour in δ 13 C. The attempt to analyse 1989-1990 was somewhat unsatisfactory, apparently because the assumption of a quasi-steady state, required by our analysis, was not satisfied sufficiently well. The main result is that global totals of oceanic versus biotic exchange are constrained primarily by the global trends of CO 2 and 13 CO 2 . The transport model constrains the regional sources and sinks but these constraints make only a small contribution to reducing the uncertainty in the global budget. We find that within the range of ≈ 1.2 Gt C y -1 our unconstrained estimates of air-sea flux are very sensitive to the choice of data that are fitted. This confirms the appropriateness of our formal error estimates based on a priori statistics. DOI: 10.1034/j.1600-0889.47.issue1.5.x
304 citations
"The utility of remotely sensed CO2 ..." refers methods in this paper
...The method we use is Bayesian synthesis inversion previously used for atmospheric trace gas studies by Enting et al. (1995) and Rayner et al. (1999)....
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TL;DR: In this paper, a tracer transport model is used to investigate the annual cycle of atmospheric CO2 concentration produced by seasonal exchanges with the terrestrial biosphere, and the results show that zonal homogeneity in surface CO2 concentrations can never be achieved at mid-latitudes where the time scale for zonal mixing is longer than the time scales for biospheric exchange.
Abstract: A three-dimensional tracer transport model is used to investigate the annual cycle of atmospheric CO2 concentration produced by seasonal exchanges with the terrestrial biosphere. The tracer model uses winds generated by a global general circulation model to advect and convect CO2; no explicit diffusion coefficients are employed. A biospheric exchange function constructed from a map of net primary productivity, and Azevedo's (1982) seasonality of CO2 uptake and release closely simulates the annual cycles at coastal stations. The results show that zonal homogeneity in surface CO2 concentrations can never be achieved at mid-latitudes where the time scale for zonal mixing is longer than the time scale for biospheric exchange. Analysis of the zonal mean balance in the lower troposphere reveals that atmospheric transport processes may alter the CO2 response to local biospheric exchanges by 50% or more. Hence year-to-year variation of the annual CO2 cycle may result from the natural variability of the atmospheric circulation as well as from changes in the sources and sinks.
186 citations
"The utility of remotely sensed CO2 ..." refers methods in this paper
...The transport model is the Goddard Institute for Space Studies (GISS) model [Fung et al. 1983]....
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TL;DR: In this article, 12 different three-dimensional atmospheric transport models have been used to model carbon dioxide concentrations due to fossil fuel burning and CO2 exchange with the terrestrial biosphere with 12 different online and off-line types.
Abstract: Carbon dioxide concentrations due to fossil fuel burning and CO2 exchange with the terrestrial biosphere have been modeled with 12 different three-dimensional atmospheric transport models. The models include both on-line and off-line types and use a variety of advection algorithms and subgrid scale parameterizations. A range of model resolutions is also represented. The modeled distributions show a large range of responses. For the experiment using the fossil fuel source, the annual mean meridional gradient at the surface varies by a factor of 2. This suggests a factor of 2 variation in the efficiency of surface interhemispheric exchange as much due to differences in model vertical transport as to horizontal differences. In the upper troposphere, zonal mean gradients within the northern hemisphere vary in sign. In the terrestrial biotic source experiment, the spatial distribution of the amplitude and the phase of the seasonal cycle of surface CO2 concentration vary little between models. However, the magnitude of the amplitudes varies similarly to the fossil case. Differences between modeled and observed seasonal cycles in the northern extratropics suggest that the terrestrial biotic source is overestimated in late spring and underestimated in winter. The annual mean response to the seasonal source also shows large differences in magnitude. The uncertainty in hemispheric carbon budgets implied by the differences in interhemispheric exchange times is comparable to those quoted by the Intergovernmental Panel on Climate Change for fossil fuel and ocean uptake and smaller than those for terrestrial fluxes. We outline approaches which may reduce this component in CO2 budget uncertainties.
174 citations
"The utility of remotely sensed CO2 ..." refers background in this paper
...In their model comparison, Law et al. (1996) showed that, on a hemispheric scale, model-model differences in vertically integrated concentration were about half those at the surface for the fossil-fuel and terrestrial biosphere sources....
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TL;DR: The GLOBALVIEW-CO2 sampling network is well suited to characterize the meridional distribution of sources and sinks but is poorly suited to separate terrestrial from oceanic sinks at the same latitude as discussed by the authors.
Abstract: The 66 stations of the GLOBALVIEW-CO2 sampling network (GLOBALVIEW-CO2: Cooperative Atmospheric Data Integration Project - Carbon Dioxide, (1997)) are located primarily remotely from continents where signals of fossil fuel consumption and biospheric exchange are diluted. It is thus not surprising that inversion studies are able to estimate terrestrial sources and sinks only to a very limited extent. The poor constraint on terrestrial fluxes propagates to the oceans and strongly limits estimates of oceanic fluxes as well, at least if no use is made of other information such as isotopic ratios. We analyze here the resolving power of the GLOBALVIEW-CO2 network, compare the efficiency of different measurement strategies, and determine optimal extensions to the present network. We find the following: (1) GLOBALVIEW-CO2 is well suited to characterize the meridional distribution of sources and sinks but is poorly suited to separate terrestrial from oceanic sinks at the same latitude. The most poorly constrained regions are South America, Africa, and southern hemispheric oceans. (2) To improve the network, observing stations need to be positioned on the continents near to the largest biospheric signals despite the large diurnal and seasonal fluctuations associated with biological activity and the dynamics of the PBL. The mixing in the atmosphere is too strong to allow positioning of stations remote from large fluxes. Our optimization results prove to be fairly insensitive to the details of model transport and the inversion model with the addition of ∼ 10 optimally positioned stations. (3) The best measurement strategy among surface observations, N-S airplane transects, and vertical profiles proves to be vertical profiles. (4) Approximately 12 optimally positioned vertical profiles or 30 surface stations in addition to GLOBALVIEW-CO2 would reduce estimate uncertainties caused by insufficient data coverage from ∼ 1 Pg C yr−1 per region to ∼ 0.2 Pg C yr−1 per region.
107 citations
"The utility of remotely sensed CO2 ..." refers methods in this paper
...This property has been previously used by Rayner et al. (1996) and Gloor et al. (2000) to suggest optimal extensions to existing networks for monthly mean observations....
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