scholarly journals The influence of megacities on global atmospheric chemistry: a modelling study

2009 ◽  
Vol 6 (3) ◽  
pp. 219 ◽  
Author(s):  
Timothy M. Butler ◽  
Mark G. Lawrence
Keyword(s):  
Atmospheric Chemistry ◽  
Urban Areas ◽  
Radiative Forcing ◽  
Transport Model ◽  
Spatial Scales ◽  
Global Scale ◽  
Reactive Nitrogen ◽  
Grid Cells ◽  
Chemical Transport Model ◽  
Future Scenario

Environmental context. Over half of the population of the world now live in urban areas, and the number of so-called ‘megacities’, with populations of ~10 million or more, is growing at a tremendous rate. We show how these patterns of urbanisation have the potential to influence the atmospheric chemical environment on a global scale, particularly through the effects of emissions from megacities on the reactive nitrogen cycle. With the growing worldwide interest in the study of the effects of megacities at all spatial scales, such as current European Union projects MEGAPOLI and CityZen, our study represents the first of many future studies that examine the effects of megacities on atmospheric chemistry on the global scale. Abstract. We present the first study of the effects of megacities on global atmospheric chemistry using a global three-dimensional chemical transport model. The effects on air quality, radiative forcing and atmospheric oxidation capacity are disproportionately smaller than the proportion of anthropogenic emissions due to megacities. Disproportionately large effects of megacities are modelled for reactive nitrogen compounds, in particular PAN (peroxy acetyl nitrate), which has increased in abundance globally by 9% due to megacities under year 2000 conditions, with 23% of the Earth experiencing an increase of 10% or more. These influences decrease under two very different future emission scenarios. Under a low-emission future scenario, the influence of megacities is generally reduced, and under a high-emission future scenario, although the local influence of megacities is increased, the geographical extent of the influence becomes smaller. In our model, the individual grid cells that contain megacities respond to the megacity emissions differently depending on their latitude. Tropical megacity grid cells generally show increased ozone year-round, while northern extratropical megacities generally show reduced ozone year-round. Better parameterisation of the sub-grid effects of megacities is an important issue for future work.

scholarly journals Impact of transport model errors on the global and regional methane emissions estimated by inverse modelling

2013 ◽  
Vol 13 (19) ◽  
pp. 9917-9937 ◽  
Author(s):  
R. Locatelli ◽  
P. Bousquet ◽  
F. Chevallier ◽  
A. Fortems-Cheney ◽  
S. Szopa ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Transport Model ◽  
Initial Conditions ◽  
Spatial Scales ◽  
Global Scale ◽  
Methane Emissions ◽  
Inverse Modelling ◽  
Model Errors ◽  
Inverse Systems ◽  
The Impact

Abstract. A modelling experiment has been conceived to assess the impact of transport model errors on methane emissions estimated in an atmospheric inversion system. Synthetic methane observations, obtained from 10 different model outputs from the international TransCom-CH4 model inter-comparison exercise, are combined with a prior scenario of methane emissions and sinks, and integrated into the three-component PYVAR-LMDZ-SACS (PYthon VARiational-Laboratoire de Météorologie Dynamique model with Zooming capability-Simplified Atmospheric Chemistry System) inversion system to produce 10 different methane emission estimates at the global scale for the year 2005. The same methane sinks, emissions and initial conditions have been applied to produce the 10 synthetic observation datasets. The same inversion set-up (statistical errors, prior emissions, inverse procedure) is then applied to derive flux estimates by inverse modelling. Consequently, only differences in the modelling of atmospheric transport may cause differences in the estimated fluxes. In our framework, we show that transport model errors lead to a discrepancy of 27 Tg yr−1 at the global scale, representing 5% of total methane emissions. At continental and annual scales, transport model errors are proportionally larger than at the global scale, with errors ranging from 36 Tg yr−1 in North America to 7 Tg yr−1 in Boreal Eurasia (from 23 to 48%, respectively). At the model grid-scale, the spread of inverse estimates can reach 150% of the prior flux. Therefore, transport model errors contribute significantly to overall uncertainties in emission estimates by inverse modelling, especially when small spatial scales are examined. Sensitivity tests have been carried out to estimate the impact of the measurement network and the advantage of higher horizontal resolution in transport models. The large differences found between methane flux estimates inferred in these different configurations highly question the consistency of transport model errors in current inverse systems. Future inversions should include more accurately prescribed observation covariances matrices in order to limit the impact of transport model errors on estimated methane fluxes.

scholarly journals Impact of aircraft NO<sub>x</sub> emissions on the atmosphere – tradeoffs to reduce the impact

2005 ◽  
Vol 5 (6) ◽  
pp. 12255-12311 ◽  
Author(s):  
M. Gauss ◽  
I. S. A. Isaksen ◽  
D. S. Lee ◽  
O. A. Søvde
Keyword(s):  
Radiative Forcing ◽  
Lower Stratosphere ◽  
Transport Model ◽  
Reactive Nitrogen ◽  
Chemical Transport Model ◽  
Reference Case ◽  
Northern Latitudes ◽  
Tropopause Region ◽  
Eu Project ◽  
The Impact

Abstract. Within the EU-project TRADEOFF, the impact of NOx (=NO+NO2) emissions from subsonic aviation upon the chemical composition of the atmosphere has been calculated with focus on changes in reactive nitrogen, ozone, and the chemical lifetime of methane. We apply a 3-D chemical transport model that includes comprehensive chemistry for both the troposphere and the stratosphere and uses various aircraft emission scenarios developed during TRADEOFF for the year 2000. The environmental effects of enhanced air traffic along polar routes and of possible changes in cruising altitude are investigated. In the reference case the model predicts aircraft-induced maximum increases of zonal-mean NOy (=total reactive nitrogen) between 156 pptv (August) and 322 pptv (May) in the tropopause region of the Northern Hemisphere. Resulting maximum increases in zonal-mean ozone vary between 3.1 ppbv in September and 7.7 ppbv in June. The lifetime of methane is calculated to decrease by 0.71%, inducing a radiative forcing of −6.4 mW/m2. Enhanced use of polar routes implies significantly larger zonal-mean ozone increases in high Northern latitudes during summer, while the effect is negligible in winter. Lowering the flight altitude leads to smaller ozone increase in the lower stratosphere and upper troposphere, and to larger ozone increase at lower altitudes. Regarding total ozone change, the degree of cancellation between these two effects depends on latitude and season, but annually and globally averaged the stratospheric decrease dominates, mainly due to washout of NOy in the troposphere, which weakens the tropospheric increase. Raising flight altitudes increases the ozone burden both in the troposphere and the lower stratosphere, primarily due to a more efficient accumulation of pollutants in the stratosphere.

Investigation of global atmospheric carbonyl sulphide between 2004 and 2018: an observational and modelling study

2020 ◽  
Author(s):  
Michael P. Cartwright ◽  
Jeremy J. Harrison ◽  
David P. Moore ◽  
John J. Remedios ◽  
Martyn P. Chipperfield ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Atmospheric Carbon Dioxide ◽  
Transport Model ◽  
Carbonyl Sulfide ◽  
Global Scale ◽  
Chemical Transport Model ◽  
Sources And Sinks ◽  
Continental Scale ◽  
Retrieval Scheme ◽  
The Relationship

&lt;p&gt;The challenge in quantifying the sources and sinks of atmospheric carbon dioxide (CO&lt;sub&gt;2&lt;/sub&gt;) is that the CO&lt;sub&gt;2&lt;/sub&gt; taken up by plants during photosynthesis cannot be distinguished from the CO&lt;sub&gt;2&lt;/sub&gt; released by plants and micro-organisms during respiration. It has been shown that carbonyl sulfide (OCS), the sulphur-containing analogue of CO&lt;sub&gt;2&lt;/sub&gt;, can be used as a proxy for photosynthesis. The relationship between the vegetative flux of OCS and CO&lt;sub&gt;2&lt;/sub&gt; has been quantified for various species of plants and ecosystems, the results of which have been used in observing the relationship on a continental scale. The aim of this project is to both quantify the location and magnitude of the sources and sinks of atmospheric OCS, and to use these data to infer photosynthetic uptake of CO&lt;sub&gt;2&lt;/sub&gt; by vegetation on a global scale.&lt;/p&gt;&lt;p&gt;A tracer version of the 3-dimensional chemical transport model TOMCAT has been adapted to include eleven different sources and sinks of OCS, including direct and indirect oceanic emissions, vegetative uptake and stratospheric photolysis. The modelled OCS (TOMCAT-OCS) distribution between 2004 and 2018 has been co-located spatially and temporally to OCS profiles measured by the Atmospheric Chemistry Experiment (ACE-FTS) over the 5 &amp;#8211; 30 km altitude, showing generally good agreement. Furthermore, surface TOMCAT-OCS has been compared to OCS measurements made at twelve NOAA-ESRL sites, across both hemispheres, showing that the model captures the seasonal cycle at the surface.&lt;/p&gt;&lt;p&gt;There have been several calls in recent years for a new satellite product of atmospheric OCS, which this project aims to satisfy. Work is ongoing to retrieve OCS total columns from measurements taken by the Infrared Atmospheric Sounding Interferometer (IASI) instruments on-board the MetOp satellites. The University of Leicester IASI Retrieval Scheme (ULIRS) has been adapted to retrieve OCS columns globally. Various case studies for different geographic regions and time periods will be presented and compared to other satellite observations.&lt;/p&gt;

scholarly journals Sunset–sunrise difference in solar occultation ozone measurements (SAGE II, HALOE, and ACE–FTS) and its relationship to tidal vertical winds

2015 ◽  
Vol 15 (2) ◽  
pp. 829-843 ◽  
Author(s):  
T. Sakazaki ◽  
M. Shiotani ◽  
M. Suzuki ◽  
D. Kinnison ◽  
J. M. Zawodny ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Seasonal Variations ◽  
Climate Model ◽  
Transport Model ◽  
Stratospheric Aerosol ◽  
Data Sets ◽  
Chemical Transport Model ◽  
Latitude Range ◽  
Solar Occultation ◽  
Vertical Winds

Abstract. This paper contains a comprehensive investigation of the sunset–sunrise difference (SSD, i.e., the sunset-minus-sunrise value) of the ozone mixing ratio in the latitude range of 10° S–10° N. SSD values were determined from solar occultation measurements based on data obtained from the Stratospheric Aerosol and Gas Experiment (SAGE) II, the Halogen Occultation Experiment (HALOE), and the Atmospheric Chemistry Experiment–Fourier transform spectrometer (ACE–FTS). The SSD was negative at altitudes of 20–30 km (−0.1 ppmv at 25 km) and positive at 30–50 km (+0.2 ppmv at 40–45 km) for HALOE and ACE–FTS data. SAGE II data also showed a qualitatively similar result, although the SSD in the upper stratosphere was 2 times larger than those derived from the other data sets. On the basis of an analysis of data from the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) and a nudged chemical transport model (the specified dynamics version of the Whole Atmosphere Community Climate Model: SD–WACCM), we conclude that the SSD can be explained by diurnal variations in the ozone concentration, particularly those caused by vertical transport by the atmospheric tidal winds. All data sets showed significant seasonal variations in the SSD; the SSD in the upper stratosphere is greatest from December through February, while that in the lower stratosphere reaches a maximum twice: during the periods March–April and September–October. Based on an analysis of SD–WACCM results, we found that these seasonal variations follow those associated with the tidal vertical winds.

scholarly journals Carbon monoxide (CO) and ethane (C<sub>2</sub>H<sub>6</sub>) trends from ground-based solar FTIR measurements at six European stations, comparison and sensitivity analysis with the EMEP model

2011 ◽  
Vol 11 (17) ◽  
pp. 9253-9269 ◽  
Author(s):  
J. Angelbratt ◽  
J. Mellqvist ◽  
D. Simpson ◽  
J. E. Jonson ◽  
T. Blumenstock ◽  
...  
Keyword(s):  
Transport Model ◽  
Global Scale ◽  
Global Model ◽  
Scale Model ◽  
Chemical Transport Model ◽  
Suitable Alternative ◽  
European Model ◽  
Time Period ◽  
Volatile Organic ◽  
Made In

Abstract. Trends in the CO andC2H6 partial columns ~0–15 km) have been estimated from four European ground-based solar FTIR (Fourier Transform InfraRed) stations for the 1996–2006 time period. The CO trends from the four stations Jungfraujoch, Zugspitze, Harestua and Kiruna have been estimated to −0.45 ± 0.16% yr−1, −1.00 ± 0.24% yr−1, −0.62 ± 0.19 % yr−1 and −0.61 ± 0.16% yr−1, respectively. The corresponding trends for C2H6 are −1.51 ± 0.23% yr−1, −2.11 ± 0.30% yr−1, −1.09 ± 0.25% yr−1 and −1.14 ± 0.18% yr−1. All trends are presented with their 2-σ confidence intervals. To find possible reasons for the CO trends, the global-scale EMEP MSC-W chemical transport model has been used in a series of sensitivity scenarios. It is shown that the trends are consistent with the combination of a 20% decrease in the anthropogenic CO emissions seen in Europe and North America during the 1996–2006 period and a 20% increase in the anthropogenic CO emissions in East Asia, during the same time period. The possible impacts of CH4 and biogenic volatile organic compounds (BVOCs) are also considered. The European and global-scale EMEP models have been evaluated against the measured CO and C2H6 partial columns from Jungfraujoch, Zugspitze, Bremen, Harestua, Kiruna and Ny-Ålesund. The European model reproduces, on average the measurements at the different sites fairly well and within 10–22% deviation for CO and 14–31% deviation for C2H6. Their seasonal amplitude is captured within 6–35% and 9–124% for CO and C2H6, respectively. However, 61–98% of the CO and C2H6 partial columns in the European model are shown to arise from the boundary conditions, making the global-scale model a more suitable alternative when modeling these two species. In the evaluation of the global model the average partial columns for 2006 are shown to be within 1–9% and 37–50% of the measurements for CO and C2H6, respectively. The global model sensitivity for assumptions made in this paper is also analyzed.

scholarly journals Impact of uncertainties in inorganic chemical rate constants on tropospheric composition and ozone radiative forcing

2017 ◽  
Author(s):  
Ben Newsome ◽  
Mat Evans
Keyword(s):  
Rate Constant ◽  
Atmospheric Chemistry ◽  
Rate Constants ◽  
Tropospheric Ozone ◽  
Radiative Forcing ◽  
Transport Model ◽  
Surface Ozone ◽  
Photolysis Rates ◽  
The Impact ◽  
Chemical Rate

Abstract. Chemical rate constants determine the composition of the atmosphere and how this composition has changed over time. They are central to our understanding of climate change and air quality degradation. Atmospheric chemistry models, whether online or offline, box, regional or global use these rate constants. Expert panels synthesise laboratory measurements, making recommendations for the rate constants that should be used. This results in very similar or identical rate constants being used by all models. The inherent uncertainties in these recommendations are, in general, therefore ignored. We explore the impact of these uncertainties on the composition of the troposphere using the GEOS-Chem chemistry transport model. Based on the JPL and IUPAC evaluations we assess 50 mainly inorganic rate constants and 10 photolysis rates, through simulations where we increase the rate of the reactions to the 1σ upper value recommended by the expert panels. We assess the impact on 4 standard metrics: annual mean tropospheric ozone burden, surface ozone and tropospheric OH concentrations, and tropospheric methane lifetime. Uncertainty in the rate constants for NO2 + OH    M →  HNO3, OH + CH4 → CH3O2 + H2O and O3 + NO → NO2 + O2 are the three largest source of uncertainty in these metrics. We investigate two methods of assessing these uncertainties, addition in quadrature and a Monte Carlo approach, and conclude they give similar outcomes. Combining the uncertainties across the 60 reactions, gives overall uncertainties on the annual mean tropospheric ozone burden, surface ozone and tropospheric OH concentrations, and tropospheric methane lifetime of 11, 12, 17 and 17 % respectively. These are larger than the spread between models in recent model inter-comparisons. Remote regions such as the tropics, poles, and upper troposphere are most uncertain. This chemical uncertainty is sufficiently large to suggest that rate constant uncertainty should be considered when model results disagree with measurement. Calculations for the pre-industrial allow a tropospheric ozone radiative forcing to be calculated of 0.412 ± 0.062 Wm−2. This uncertainty (15 %) is comparable to the inter-model spread in ozone radiative forcing found in previous model-model inter-comparison studies where the rate constants used in the models are all identical or very similar. Thus the uncertainty of tropospheric ozone radiative forcing should expanded to include this additional source of uncertainty. These rate constant uncertainties are significant and suggest that refinement of supposedly well known chemical rate constants should be considered alongside other improvements to enhance our understanding of atmospheric processes.

scholarly journals Key factors affecting single scattering albedo calculation: Implications for aerosol climate forcing

2017 ◽  
Author(s):  
Duseong S. Jo ◽  
Rokjin J. Park ◽  
Jaein I. Jeong ◽  
Gabriele Curci ◽  
Hyung-Min Lee ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Radiative Forcing ◽  
Transport Model ◽  
Geometric Mean ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Geometric Standard Deviation ◽  
Physical Parameters ◽  
Chemical Transport Model ◽  
Aerosol Mass

Abstract. Single Scattering Albedo (SSA), the ratio of scattering efficiency to total extinction efficiency, is an essential parameter used to estimate the Direct Radiative Forcing (DRF) of aerosols. However, SSA is one of the large contributors to the uncertainty of DRF estimations. In this study, we examined the sensitivity of SSA calculations to the physical properties of absorbing aerosols, in particular, Black Carbon (BC), Brown Carbon (BrC), and dust. We used GEOS-Chem 3-D global chemical transport model (CTM) simulations and a post-processing tool for the aerosol optical properties (FlexAOD). The model and input parameters were evaluated by comparison against the observed aerosol mass concentrations and the Aerosol Optical Depth (AOD) values obtained from global surface observation networks such as the global Aerosol Mass Spectrometer (AMS) dataset, the Surface Particulate Matter Network (SPARTAN), and the Aerosol Robotic Network (AERONET). The model was generally successful in reproducing the observed variability of both the Particulate Matter 2.5 μm (PM2.5) and AOD (R ~ 0.76) values, although it underestimated the magnitudes by approximately 20 %. Our sensitivity tests of the SSA calculation revealed that the aerosol physical parameters, which have generally received less attention than the aerosol mass loadings, can cause large uncertainties in the resulting DRF estimation. For example, large variations in the calculated BC absorption may result from slight changes of the geometric mean radius, geometric standard deviation, real and imaginary refractive indices, and density. The inclusion of BrC and observationally-constrained dust size distributions also significantly affected the SSA, and resulted in a remarkable improvement for the simulated SSA at 440 nm (bias was reduced by 44–49 %) compared with the AERONET observations. Based on the simulations performed during this study, we found that the global aerosol direct radiative effect was increased by 10 % after the SSA bias was reduced.

scholarly journals Sensitivity of the recent methane budget to LMDz sub-grid scale physical parameterizations

2015 ◽  
Vol 15 (8) ◽  
pp. 11853-11888
Author(s):  
R. Locatelli ◽  
P. Bousquet ◽  
M. Saunois ◽  
F. Chevallier ◽  
C. Cressot
Keyword(s):  
Satellite Data ◽  
Transport Model ◽  
Deep Convection ◽  
Chemical Transport ◽  
Global Scale ◽  
Methane Emissions ◽  
Inverse Modelling ◽  
Chemical Transport Model ◽  
Methane Budget ◽  
Physical Parameterizations

Abstract. With the densification of surface observing networks and the development of remote sensing of greenhouse gases from space, estimations of methane (CH4) sources and sinks by inverse modelling face new challenges. Indeed, the chemical transport model used to link the flux space with the mixing ratio space must be able to represent these different types of constraints for providing consistent flux estimations. Here we quantify the impact of sub-grid scale physical parameterization errors on the global methane budget inferred by inverse modelling using the same inversion set-up but different physical parameterizations within one chemical-transport model. Two different schemes for vertical diffusion, two others for deep convection, and one additional for thermals in the planetary boundary layer are tested. Different atmospheric methane datasets are used as constraints (surface observations or satellite retrievals). At the global scale, methane emissions differ, on average, from 4.1 Tg CH4 per year due to the use of different sub-grid scale parameterizations. Inversions using satellite total-column retrieved by GOSAT satellite are less impacted, at the global scale, by errors in physical parameterizations. Focusing on large-scale atmospheric transport, we show that inversions using the deep convection scheme of Emanuel (1991) derive smaller interhemispheric gradient in methane emissions. At regional scale, the use of different sub-grid scale parameterizations induces uncertainties ranging from 1.2 (2.7%) to 9.4% (14.2%) of methane emissions in Africa and Eurasia Boreal respectively when using only surface measurements from the background (extended) surface network. When using only satellite data, we show that the small biases found in inversions using GOSAT-CH4 data and a coarser version of the transport model were actually masking a poor representation of the stratosphere–troposphere gradient in the model. Improving the stratosphere–troposphere gradient reveals a larger bias in GOSAT-CH4 satellite data, which largely amplifies inconsistencies between surface and satellite inversions. A simple bias correction is proposed. The results of this work provide the level of confidence one can have for recent methane inversions relatively to physical parameterizations included in chemical-transport models.

scholarly journals Ethane, ethyne and carbon monoxide concentrations in the upper troposphere and lower stratosphere from ACE and GEOS-Chem: a comparison study

2011 ◽  
Vol 11 (4) ◽  
pp. 13099-13139 ◽  
Author(s):  
G. González Abad ◽  
N. D. C. Allen ◽  
P. F. Bernath ◽  
C. D. Boone ◽  
S. D. McLeod ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
Atmospheric Chemistry ◽  
Transport Model ◽  
Chemical Mechanism ◽  
Chemical Transport Model ◽  
Spectrometer Data ◽  
Chemistry Experiment ◽  
Global Mean ◽  
Tropospheric Concentrations ◽  
Good Agreement

Abstract. Near global upper tropospheric concentrations of carbon monoxide (CO), ethane (C2H6) and ethyne (C2H2) from ACE (Atmospheric Chemistry Experiment) Fourier transform spectrometer on board the Canadian satellite SCISAT-1 are presented and compared with the output from the Chemical Transport Model (CTM) GEOS-Chem. The retrievals of ethane and ethyne from ACE have been improved for this paper by using new sets of microwindows compared with those for previous versions of ACE data. With the improved ethyne retrieval we have been able to produce a near global upper tropospheric distribution of C2H2 from space. Carbon monoxide, ethane and ethyne concentrations retrieved using ACE spectra show the expected seasonality linked to variations in the anthropogenic emissions and destruction rates as well as seasonal biomass burning activity. The GEOS-Chem model was run using the dicarbonyl chemistry suite, an extended chemical mechanism in which ethyne is treated explicitly. Seasonal cycles observed from satellite data are well reproduced by the model output, however the simulated CO concentrations are found to be systematically biased low over the Northern Hemisphere. An average negative global mean bias of 12% and 7% of the model relative to the satellite observations has been found for CO and C2H6 respectively and a positive global mean bias of 1% has been found for C2H2. ACE data are compared for validation purposes with MkIV spectrometer data and Global Tropospheric Experiment (GTE) TRACE-A campaign data showing good agreement with all of them.

scholarly journals Spatial and temporal resolution of carbon flux estimates for 1983–2002

2007 ◽  
Vol 4 (6) ◽  
pp. 4697-4756 ◽  
Author(s):  
L. M. P. Bruhwiler ◽  
A. M. Michalak ◽  
P. P. Tans
Keyword(s):  
North America ◽  
Temporal Resolution ◽  
Carbon Flux ◽  
Seasonal Cycle ◽  
Transport Model ◽  
Spatial Scales ◽  
Carbon Fluxes ◽  
Chemical Transport Model ◽  
Data Product ◽  
Zonal Average

Abstract. We discuss the spatial and temporal resolution of monthly carbon flux estimates for the period 1983–2002 using a fixed-lag Kalman Smoother technique with a global chemical transport model, and the GLOBALVIEW data product. The observational network has expanded substantially over this period, and we the improvement in the constraints provided flux estimates by observations for the 1990's in comparison to the 1980's. The estimated uncertainties also decrease as observational coverage expands. In this study, we use the Globalview data product for a network that changes every 5 y, rather than using a small number of continually-operating sites (fewer observational constraints) or a large number of sites, some of which may consist almost entirely of extrapolated data. We show that the discontinuities resulting from network changes reflect uncertainty due to a sparse and variable network. This uncertainty effectively limits the resolution of trends in carbon fluxes. The ability of the inversion to distinguish, or resolve, carbon fluxes at various spatial scales is examined using a diagnostic known as the resolution kernel. We find that the global partition between land and ocean fluxes is well-resolved even for the very sparse network of the 1980's, although prior information makes a significant contribution to the resolution. The ability to distinguish zonal average fluxes has improved significantly since the 1980's, especially for the tropics, where the zonal ocean and land biosphere fluxes can be distinguished. Care must be taken when interpreting zonal average fluxes, however, since the lack of air samples for some regions in a zone may result in a large influence from prior flux estimates for these regions. We show that many of the TransCom 3 source regions are distinguishable throughout the period over which estimates are produced. Examples are Boreal and Temperate North America. The resolution of fluxes from Europe and Australia has greatly improved since the 1990's. Other regions, notably Tropical South America and the Equatorial Atlantic remain practically unresolved. Comparisons of the average seasonal cycle of the estimated carbon fluxes with the seasonal cycle of the prior flux estimates reveals a large adjustment of the summertime uptake of carbon for Boreal Eurasia, and an earlier onset of springtime uptake for Temperate North America. In addition, significantly larger seasonal cycles are obtained for some ocean regions, such as the Northern Ocean, North Pacific, North Atlantic and Western Equatorial Pacific, regions that appear to be well-resolved by the inversion.

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