Satellite observations indicate substantial spatiotemporal variability in biomass burning NOx emission factors for South America
Castellanos, P. ; Boersma, K.F. ; Werf, G.R. van de - \ 2014
Atmospheric Chemistry and Physics 14 (2014). - ISSN 1680-7316 - p. 3929 - 3943.
ozone monitoring instrument - fire emissions - trace gases - tropospheric chemistry - chemical-composition - nitrogen-dioxide - tropical forest - b experiment - model tm5 - brazil
Biomass burning is an important contributor to global total emissions of NOx (NO+NO2). Generally bottom-up fire emissions models calculate NOx emissions by multiplying fuel consumption estimates with static biome-specific emission factors, defined in units of grams of NO per kilogram of dry matter consumed. Emission factors are a significant source of uncertainty in bottom-up fire emissions modeling because relatively few observations are available to characterize the large spatial and temporal variability of burning conditions. In this paper we use NO2 tropospheric column observations from the Ozone Monitoring Instrument (OMI) from the year 2005 over South America to calculate monthly NOx emission factors for four fire types: deforestation, savanna/grassland, woodland, and agricultural waste burning. In general, the spatial patterns in NOx emission factors calculated in this work are consistent with emission factors derived from in situ measurements from the region but are more variable than published biome-specific global average emission factors widely used in bottom-up fire emissions inventories such as the Global Fire Emissions Database (GFED). Satellite-based NOx emission factors also indicate substantial temporal variability in burning conditions. Overall, we found that deforestation fires have the lowest NOx emission factors, on average 30% lower than the emission factors used in GFED v3. Agricultural fire NOx emission factors were the highest, on average a factor of 1.8 higher than GFED v3 values. For savanna, woodland, and deforestation fires, early dry season NOx emission factors were a factor of ~1.5–2 higher than late dry season emission factors. A minimum in the NOx emission factor seasonal cycle for deforestation fires occurred in August, the time period of severe drought in South America in 2005, supporting the hypothesis that prolonged dry spells may lead to an increase in the contribution of smoldering combustion from large-diameter fuels, offsetting the higher combustion efficiency of dryer fine fuels. We evaluated the OMI-derived NOx emission factors with SCIAMACHY NO2 tropospheric column observations and found improved model performance in regions dominated by fire emissions.
Reassessing the variability in atmospheric H2 using the two-way nested TM5 model
Pieterse, G. ; Krol, M.C. ; Batenburg, A.M. ; Brenninkmeijer, C.A. ; Popa, M.E. ; O'Doherty, S. ; Grant, A. ; Steele, L.P. ; Krummel, P.B. ; Langenfelds, R.L. ; Wang, H.J. ; Vermeulen, A.T. ; Schmidt, M. ; Yver, C. ; Jordan, A. ; Engel, A. ; Fisher, R.E. ; Lowry, D. ; Nisbet, E.G. ; Reimann, S. ; Vollmer, M.K. ; Steinbacher, M. ; Hammer, S. ; Forster, G. ; Sturges, W.T. ; Rockmann, T. - \ 2013
Journal of Geophysical Research: Atmospheres 118 (2013)9. - ISSN 2169-897X - p. 3764 - 3780.
dry deposition parameterization - stable isotopic composition - general-circulation model - global hydrogen economy - molecular-hydrogen - trace gases - environmental-impact - dissolved hydrogen - seasonal-variation - data assimilation
This work reassesses the global atmospheric budget of H2 with the TM5 model. The recent adjustment of the calibration scale for H2 translates into a change in the tropospheric burden. Furthermore, the ECMWF Reanalysis-Interim (ERA-Interim) data from the European Centre for Medium-Range Weather Forecasts (ECMWF) used in this study show slower vertical transport than the operational data used before. Consequently, more H2 is removed by deposition. The deposition parametrization is updated because significant deposition fluxes for snow, water, and vegetation surfaces were calculated in our previous study. Timescales of 1-2h are asserted for the transport of H2 through the canopies of densely vegetated regions. The global scale variability of H2 and [DH2] is well represented by the updated model. H2 is slightly overestimated in the Southern Hemisphere because too little H2 is removed by dry deposition to rainforests and savannahs. The variability in H2 over Europe is further investigated using a high-resolution model subdomain. It is shown that discrepancies between the model and the observations are mainly caused by the finite model resolution. The tropospheric burden is estimated at 165 +/- 8TgH2. The removal rates of H2 by deposition and photochemical oxidation are estimated at 53 +/- 4 and 23 +/- 2TgH2/yr, resulting in a tropospheric lifetime of 2.2 +/- 0.2year.
Emission ratio and isotopic signatures of molecular hydrogen emissions from tropical biomass burning
Haumann, F.A. ; Batenburg, A.M. ; Pieterse, G. ; Gerbig, C. ; Krol, M.C. ; Rockmann, T. - \ 2013
Atmospheric Chemistry and Physics 13 (2013)18. - ISSN 1680-7316 - p. 9401 - 9413.
atmospheric hydrogen - assimilation system - land-surface - amazon basin - trace gases - tall tower - model tm5 - h-2 - chemistry - plants
In this study, we identify a biomass-burning signal in molecular hydrogen (H-2) over the Amazonian tropical rainforest. To quantify this signal, we measure the mixing ratios of H-2 and several other species as well as the H-2 isotopic composition in air samples that were collected in the BARCA (Balanco Atmosferico Regional de Carbono na Amazonia) aircraft campaign during the dry season. We derive a relative H-2 emission ratio with respect to carbon monoxide (CO) of 0.31 +/- 0.04 ppb ppb(-1) and an isotopic source signature of -280 +/- 41 parts per thousand in the air masses influenced by tropical biomass burning. In order to retrieve a clear source signal that is not influenced by the soil uptake of H-2, we exclude samples from the atmospheric boundary layer. This procedure is supported by data from a global chemistry transport model. The Delta H-2/Delta CO emission ratio is significantly lower than some earlier estimates for the tropical rainforest. In addition, our results confirm the lower values of the previously conflicting estimates of the H-2 isotopic source signature from biomass burning. These values for the emission ratio and isotopic source signatures of H-2 from tropical biomass burning can be used in future bottom-up and top-down approaches aiming to constrain the strength of the biomass-burning source for H-2. Hitherto, these two quantities relied only on combustion experiments or on statistical relations, since no direct signal had been obtained from in-situ observations.
What could have caused pre-industrial biomass burning emissions to exceed current rates?
Werf, G.R. van der; Peters, W. ; Leeuwen, T.T. van; Giglio, L. - \ 2013
Climate of the Past 9 (2013)1. - ISSN 1814-9324 - p. 289 - 306.
rain-forest fires - past 2 millennia - amazonian forests - southern africa - trace gases - model tm5 - land-use - carbon - 20th-century - climate
Recent studies based on trace gas mixing ratios in ice cores and charcoal data indicate that biomass burning emissions over the past millennium exceeded contemporary emissions by up to a factor of 4 for certain time periods. This is surprising because various sources of biomass burning are linked with population density, which has increased over the past centuries. We have analysed how emissions from several landscape biomass burning sources could have fluctuated to yield emissions that are in correspondence with recent results based on ice core mixing ratios of carbon monoxide (CO) and its isotopic signature measured at South Pole station (SPO). Based on estimates of contemporary landscape fire emissions and the TM5 chemical transport model driven by present-day atmospheric transport and OH concentrations, we found that CO mixing ratios at SPO are more sensitive to emissions from South America and Australia than from Africa, and are relatively insensitive to emissions from the Northern Hemisphere. We then explored how various landscape biomass burning sources may have varied over the past centuries and what the resulting emissions and corresponding CO mixing ratio at SPO would be, using population density variations to reconstruct sources driven by humans (e.g., fuelwood burning) and a new model to relate savanna emissions to changes in fire return times. We found that to match the observed ice core CO data, all savannas in the Southern Hemisphere had to burn annually, or bi-annually in combination with deforestation and slash and burn agriculture exceeding current levels, despite much lower population densities and lack of machinery to aid the deforestation process. While possible, these scenarios are unlikely and in conflict with current literature. However, we do show the large potential for increased emissions from savannas in a pre-industrial world. This is mainly because in the past, fuel beds were probably less fragmented compared to the current situation; satellite data indicates that the majority of savannas have not burned in the past 10 yr, even in Africa, which is considered "the burning continent". Although we have not considered increased charcoal burning or changes in OH concentrations as potential causes for the elevated CO concentrations found at SPO, it is unlikely they can explain the large increase found in the CO concentrations in ice core data. Confirmation of the CO ice core data would therefore call for radical new thinking about causes of variable global fire rates over recent centuries
Modelling the partitioning of ammonium nitrate in the convective boundary layer
Brugh, J.M.J. Aan de; Henzing, J.S. ; Schaap, M. ; Morgan, W.T. ; Heerwaarden, C.C. van; Weijers, E.P. ; Coe, H. ; Krol, M.C. - \ 2012
Atmospheric Chemistry and Physics 12 (2012)6. - ISSN 1680-7316 - p. 3005 - 3023.
thermodynamic-equilibrium model - jet aerosol collector - inorganic aerosol - air-quality - particulate matter - trace gases - europe - spectrometer - mobility - field
An explanatory model study is presented on semi-volatile secondary inorganic aerosols on three clear days in May 2008 during the IMPACT campaign at the Cabauw tower in the Netherlands. A single column model in combination with the equilibrium aerosol model ISORROPIA is used. This model uses surface observations from IMPACT and calculates the gas-aerosol partitioning of ammonium nitrate. The calculated gas-aerosol equilibrium overestimates the gas phase fraction during daytime, and overestimates the aerosol phase fraction during night-time. This discrepancy can partly be solved when the approach of the gas-aerosol equilibrium is forced to proceed with a delay timescale of up to two hours. Although it is shown that the delay itself has a small effect, the most important effect is caused by the mixing of air from higher altitudes at which the equilibrium is shifted to the aerosol phase. Thus, vertical mixing is shown to have a significant influence on the calculated partitioning at the surface. On some occasions, the correspondence to the observed partitioning improves dramatically. Even though gas-aerosol partitioning of ammonium nitrate is not instantaneous, observations show that a different equilibrium in the upper boundary layer causes aerosol ammonium nitrate concentrations to increase with altitude. Our model calculates similar vertical gradients depending on the assumed speed of gas-aerosol equilibrium. The calculated optical properties of the aerosol show a similar behaviour. The aerosol optical properties depend on the aerosol size distribution both directly, because light scattering depends on particle size, and indirectly, because the equilibration timescale depends on the aerosol sizes. Future studies should therefore focus on a fully size-resolved treatment of the gas-aerosol partitioning. Finally, coarser-resolution models may treat the gas-aerosol equilibrium of ammonium nitrate by calculating the equilibrium with a temperature and humidity sampled at a different altitude. We found that the equilibrium at an altitude of 200 m (night) up to 600 m (day) is representative for the partitioning of ammonium nitrate at the surface in the beginning of May 2008
Spatial distribution of Delta(CO2)-C-14 across Eurasia: measurements from the TROICA-8 expedition
Turnbull, J.C. ; Miller, J.B. ; Lehman, S.J. ; Hurst, D. ; Peters, W. - \ 2009
Atmospheric Chemistry and Physics 9 (2009)1. - ISSN 1680-7316 - p. 175 - 187.
fossil-fuel co2 - trans-siberian railroad - nuclear-power-plants - carbon-dioxide - (co2)-c-14 observations - atmospheric co2 - united-states - trace gases - model tm5 - c-14
Because fossil fuel derived CO2 is the only source of atmospheric CO2 that is devoid of 14C, atmospheric measurements of delta14CO2 can be used to constrain fossil fuel emission estimates at local and regional scales. However, at the continental scale, uncertainties in atmospheric transport and other sources of variability in delta14CO2 may influence the fossil fuel detection capability. We present a set of delta14CO2 observations from the train-based TROICA-8 expedition across Eurasia in March-April 2004. Local perturbations in delta14CO2 are caused by easily identifiable sources from nuclear reactors and localized pollution events. The remaining data show an increase in delta14CO2 from Western Russia (40° E) to Eastern Siberia (120° E), consistent with depletion in 14CO2 caused by fossil fuel CO2 emissions in heavily populated Europe, and gradual dispersion of the fossil fuel plume across Northern Asia. Other trace gas species which may be correlated with fossil fuel CO2 emissions, including carbon monoxide, sulphur hexafluoride, and perchloroethylene, were also measured and the results compared with the delta14CO2 measurements. The sulphur hexafluoride longitudinal gradient is not significant relative to the measurement uncertainty. Carbon monoxide and perchloroethylene show large-scale trends of enriched values in Western Russia and decreasing values in Eastern Siberia, consistent with fossil fuel emissions, but exhibit significant spatial variability, especially near their primary sources in Western Russia. The clean air delta14CO2 observations are compared with simulated spatial gradients from the TM5 atmospheric transport model. We show that the change in delta14CO2 across the TROICA transect is due almost entirely to emissions of fossil fuel CO2, but that the magnitude of this delta14CO2 gradient is relatively insensitive to modest uncertainties in the fossil fuel flux. In contrast, the delta14CO2 gradient is more sensitive to the modeled representation of vertical mixing, suggesting that delta14CO2 may be a useful tracer for training mixing in atmospheric transport models.
Global reactive nitrogen deposition from lightning NOx
Shepon, A. ; Gildor, H. ; Labrador, L.J. ; Butler, T. ; Ganzeveld, L.N. ; Lawrence, M.G. - \ 2007
Journal of Geophysical Research: Atmospheres 112 (2007). - ISSN 2169-897X - 14 p.
general-circulation model - dry deposition - atmospheric chemistry - organic nitrogen - climate-change - trace gases - distributions - parameterization - cycle - emissions
We present results of the deposition of nitrogen compounds formed from lightning (LNO x ) using the global chemical transport Model of Atmospheric Transport and Chemistry¿Max Planck Institute for Chemistry version. The model indicates an approximately equal deposition of LNO x in both terrestrial and oceanic ecosystems, primarily in the tropics and midlatitudes open ocean, despite much higher intensities of lightning flashes above landmasses. The highest values of deposition are due to wet convective deposition, with highest values concentrated in the tropical continents. Nonconvective wet deposition, associated with large-scale weather patterns, occurs over large areas of the ocean amid lower values per square meter, manifesting the long-range transport of NO y , including long-lived species such as HNO3 at high altitudes and PAN. Dry deposition is concentrated primarily above landmasses, yet oceanic deposition over wide areas is still observed. Combined together, the total LNO x deposition exhibits maximal influx values over land, whereas oceanic deposition over wider areas renders the integrated deposition over both ecosystems almost identical. Peaks of terrestrial deposition values (located in Africa, South America, and Asia) show seasonal variability by meridionally penetrating the northern or southern midlatitude following the corresponding summer hemisphere, in accordance with the migration of LNO x production sites. On land, wet and dry deposition rates are more or less equal with a small bias toward wet deposition, whereas above the ocean, wet deposition is markedly higher because of a small water uptake efficiency and relatively small surface roughness. Further work of modeling additional species and obtaining more information on different compounds is required
Challenges in quantifying biosphere-atmosphere exchange of nitrogen species.
Sutton, M.A. ; Nemitz, E. ; Erisman, J.W. ; Beier, C. ; Butterbach-Bahl, K. ; Cellier, P. ; Vries, W. de; Cotrufo, F. ; Skiba, U. ; Marco, C. Di; Jones, S. ; Laville, P. ; Soussana, J.F. ; Loubet, B. ; Twigg, M. ; Famulari, D. ; Whitehead, J. ; Gallagher, M.W. ; Neftel, A. ; Flechard, C.R. ; Herrmann, B. ; Calanca, P.L. ; Schjoerring, J.K. ; Daemmgen, U. ; Horvath, L. ; Tang, Y.S. ; Emmet, B.A. ; Tietema, A. ; Penuelas, J. ; Kesik, M. ; Brueggemann, N. ; Pilegaard, K. ; Vesala, T. ; Campbell, C.L. ; Olesen, J.E. ; Dragosits, U. ; Theobald, M.R. ; Levy, P. ; Mobbs, D.C. ; Milne, R. ; Viovy, N. ; Vuichard, N. ; Smith, J.U. ; Smith, P. ; Bergamaschi, P. ; Fowler, D. ; Reis, S. Dos - \ 2007
Environmental Pollution 150 (2007)1. - ISSN 0269-7491 - p. 125 - 139.
gas-particle interactions - surface-exchange - simulation-model - ammonia exchange - dutch heathland - climate-change - oxide fluxes - trace gases - deposition - soil
Recent research in nitrogen exchange with the atmosphere has separated research communities according to N form. The integrated perspective needed to quantify the net effect of N on greenhouse-gas balance is being addressed by the NitroEurope Integrated Project (NEU). Recent advances have depended on improved methodologies, while ongoing challenges include gas¿aerosol interactions, organic nitrogen and N2 fluxes. The NEU strategy applies a 3-tier Flux Network together with a Manipulation Network of global-change experiments, linked by common protocols to facilitate model application. Substantial progress has been made in modelling N fluxes, especially for N2O, NO and bi-directional NH3 exchange. Landscape analysis represents an emerging challenge to address the spatial interactions between farms, fields, ecosystems, catchments and air dispersion/deposition. European up-scaling of N fluxes is highly uncertain and a key priority is for better data on agricultural practices. Finally, attention is needed to develop N flux verification procedures to assess compliance with international protocols.
An improved Kalman Smoother for atmospheric inversions
Bruhwiler, L. ; Michalak, A. ; Peters, W. ; Baker, D. ; Tans, P.P. - \ 2005
Atmospheric Chemistry and Physics 5 (2005). - ISSN 1680-7316 - p. 2691 - 2702.
carbon-dioxide - trace gases - co2 sources - transport - sensitivity - models - sinks - emissions - scheme - cycle
We explore the use of a fixed-lag Kalman smoother for sequential estimation of atmospheric carbon dioxide fluxes. This technique takes advantage of the fact that most of the information about the spatial distribution of sources and sinks is observable within a few months to half of a year of emission. After this period, the spatial structure of sources is diluted by transport and cannot significantly constrain flux estimates. We therefore describe an estimation technique that steps through the observations sequentially, using only the subset of observations and modeled transport fields that most strongly constrain the fluxes at a particular time step. Estimates of each set of fluxes are sequentially updated multiple times, using measurements taken at different times, and the estimates and their uncertainties are shown to quickly converge. Final flux estimates are incorporated into the background state of CO2 and transported forward in time, and the final flux uncertainties and covariances are taken into account when estimating the covariances of the fluxes still being estimated. The computational demands of this technique are greatly reduced in comparison to the standard Bayesian synthesis technique where all observations are used at once with transport fields spanning the entire period of the observations. It therefore becomes possible to solve larger inverse problems with more observations and for fluxes discretized at finer spatial scales. We also discuss the differences between running the inversion simultaneously with the transport model and running it entirely off-line with pre-calculated transport fields. We find that the latter can be done with minimal error if time series of transport fields of adequate length are pre-calculated.