bluuebunny/crossref_metadata_2025_split huggingface dataset:
Impact of biogenic hydrocarbons on tropospheric chemistry: results from a global chemistry-climate model
Authors: Folberth G. A. , Hauglustaine D. A. , Lathière J. , Brocheton F. 
Published: April 2010

Abstract. We present a description and evaluation of LMDz-INCA, a global three-dimensional chemistry-climate model, pertaining to its recently developed NMHC version. In this substantially extended version of the model a comprehensive representation of the photochemistry of non-methane hydrocarbons (NMHC) and volatile organic compounds (VOC) from biogenic, anthropogenic, and biomass-burning sources has been included. The tropospheric annual mean methane (9.2 years) and methylchloroform (5.5 years) chemical lifetimes are well within the range of previous modelling studies and are in excellent agreement with estimates established by means of global observations. The model provides a reasonable simulation of the horizontal and vertical distribution and seasonal cycle of CO and key non-methane VOC, such as acetone, methanol, and formaldehyde as compared to observational data from several ground stations and aircraft campaigns. LMDz-INCA in the NMHC version reproduces tropospheric ozone concentrations fairly well throughout most of the troposphere. The model is applied in several sensitivity studies of the biosphere-atmosphere photochemical feedback. The impact of surface emissions of isoprene, acetone, and methanol is studied. These experiments show a substantial impact of isoprene on tropospheric ozone and carbon monoxide concentrations revealing an increase in surface O3 and CO levels of up to 30 ppbv and 60 ppbv, respectively. Isoprene also appears to significantly impact the global OH distribution resulting in a decrease of the global mean tropospheric OH concentration by approximately 0.9×105 molecules cm−3 or roughly 10% and an increase in the global mean tropospheric methane lifetime by approximately four months. A global mean ozone net radiative forcing due to the isoprene induced increase in the tropospheric ozone burden of 0.09W m−2 is found. The key role of isoprene photooxidation in the global tropospheric redistribution of NOx is demonstrated. LMDz-INCA calculates an increase of PAN surface mixing ratios ranging from 75 to 750 pptv and 10 to 250 pptv during northern hemispheric summer and winter, respectively. Acetone and methanol are found to play a significant role in the upper troposphere/lower stratosphere (UT/LS) budget of peroxy radicals. Calculations with LMDz-INCA show an increase in HOx concentrations region of 8 to 15% and 10 to 15% due to methanol and acetone biogenic surface emissions, respectively. The model has been used to estimate the global tropospheric CO budget. A global CO source of 3019 TgCO yr−1 is estimated. This source divides into a primary source of 1533 TgCO yr−1 and secondary source of 1489 TgCO yr−1 deriving from VOC photooxidation. Global VOC-to-CO conversion efficiencies of 90% for methane and between 20 and 45% for individual VOC are calculated by LMDz-INCA.
Testing our understanding of Arctic denitrification using MIPAS-E satellite measurements in winter 2002/3
Authors: Davies S. , Mann G. W. , Carslaw K. S. , Chipperfield M. P. , Remedios J. J. , Allen G. , Waterfall A. M. , Spang R. , Toon G. C. 
Published: April 2010

Abstract. Observations of gas-phase HNO3 and N2O in the polar stratosphere from the Michelson Interferometer for Passive Atmospheric Sounding aboard the ENVISAT satellite (MIPAS-E) were made during the cold Arctic winter of 2002/3. Vortex temperatures were unusually low in early winter and remained favourable for polar stratospheric cloud formation and denitrification until mid-January. MIPAS-E observations provide the first dataset with sufficient coverage of the polar vortex in mid-winter which enables a reasonable estimate of the timing of onset and spatial distribution of denitrification of the Arctic lower stratosphere to be performed. We use the observations from MIPAS-E to test the evolution of denitrification in the DLAPSE (Denitrification by Lagrangian Particle Sedimentation) microphysical denitrification model coupled to the SLIMCAT chemical transport model. In addition, the predicted denitrification from a simple equilibrium nitric acid trihydrate-based scheme is also compared with MIPAS-E. Modelled denitrification is compared with in-vortex NOy and N2O observations from the balloon-borne MarkIV interferometer in mid-December. Denitrification was clearly observed by MIPAS-E in mid-December 2002 and reached 80% in the core of the vortex by early January 2003. The DLAPSE model is broadly able to capture both the timing of onset and the spatial distribution of the observed denitrification. A simple thermodynamic equilibrium scheme is able to reproduce the observed denitrification in the core of the vortex but overestimates denitrification closer to the vortex edge. This study also suggests that the onset of denitrification in simple thermodynamic schemes may be earlier than in the MIPAS-E observations.
Global estimation of burned area using MODIS active fire observations
Authors: Giglio L. , van der Werf G. R. , Randerson J. T. , Collatz G. J. , Kasibhatla P. 
Published: April 2010

Abstract. We present a method for estimating monthly burned area globally at 1° spatial resolution using Terra MODIS data and ancillary vegetation cover information. Using regression trees constructed for 14 different global regions, MODIS active fire observations were calibrated to ''true'' burned area estimates derived from 500-m MODIS imagery based on the conventional assumption that burned area is proportional to counts of fire pixels. Unlike earlier methods, we allow the constant of proportionality to vary as a function of tree and herbaceous vegetation cover, and the mean size of monthly cumulative fire-pixel clusters. In areas undergoing active deforestation, we implemented a subsequent correction based on tree cover information and a simple measure of fire persistence. Regions showing good agreement between predicted and observed burned area included Boreal Asia, Central Asia, Europe, and Temperate North America, where the estimates produced by the regression trees were relatively accurate and precise. Poorest agreement was found for southern-hemisphere South America, where predicted values of burned area are both inaccurate and imprecise; this is most likely a consequence of multiple factors that include extremely persistent cloud cover, and degradation of the quality of the 500-m burned area maps used for calibration. Application of our approach to the nine remaining regions yielded comparatively accurate, but less precise, estimates of monthly burned area. We applied the regional regression trees to the entire archive of Terra MODIS fire data to produce a monthly global burned area data set spanning late 2000 through mid-2005. Annual totals derived from this approach showed good agreement with independent annual estimates available for nine Canadian provinces, the United States, and Russia. With our data set we estimate the global annual burned area for the years 2001–2004 to vary between 2.97 million and 3.74 million km2, with the maximum occurring in 2001. These coarse-resolution burned area estimates may serve as a useful interim product until long-term burned area data sets become available.
Estimating the NOx produced by lightning from GOME and NLDN data: a case study in the Gulf of Mexico
Authors: Beirle S. , Spichtinger N. , Stohl A. , Cummins K. L. , Turner T. , Boccippio D. , Cooper O. R. , Wenig M. , Grzegorski M. , Platt U. , Wagner T. 
Published: April 2010

Abstract. Nitrogen oxides (NOx=NO+NO2) play an important role in tropospheric chemistry, in particular in catalytic ozone production. Lightning provides a natural source of nitrogen oxides, dominating the production in the tropical upper troposphere, with strong impact on tropospheric ozone and the atmosphere's oxidizing capacity. Recent estimates of lightning produced NOx (LNOx) are of the order of 5 Tg [N] per year with still high uncertainties in the range of one order of magnitude. The Global Ozone Monitoring Experiment (GOME) on board the ESA-satellite ERS-2 allows the retrieval of tropospheric vertical column densities (TVCDs) of NO2 on a global scale. Here we present the GOME NO2 measurement directly over a large convective system over the Gulf of Mexico. Simultaneously, cloud-to-ground (CG) flashes are counted by the U.S. National Lightning Detection Network (NLDNTM), and extrapolated to include intra-cloud (IC)+CG flashes based on a climatological IC:CG ratio derived from NASA's space-based lightning sensors. A series of 14 GOME pixels shows largely enhanced TVCDs over thick and high clouds, coinciding with strong lightning activity. The enhancements can not be explained by transport of anthropogenic NOx and must be due to fresh production of LNOx. A quantitative analysis, accounting in particular for the visibility of LNOx from satellite, yields a LNOx production of 77 (27–230) moles of NOx, or 1.1 (0.4–3.2) kg [N], per flash. If simply extrapolated, this corresponds to a global LNOx production of 1.5 (0.5–4.5) Tg [N]/yr.
Impacts of using reformulated and oxygenated fuel blends on the regional air quality of the upper Rhine valley
Authors: Vinuesa J.-F. , Mirabel Ph. , Ponche J.-L. 
Published: April 2010

Abstract. The effects of using three alternative gasoline fuel blends on regional air quality of the upper Rhine valley have been investigated. The first of the tested fuels is oxygenated by addition of ethyl-tertio-butyl ether (ETBE), the second is based on a reformulation of its composition and the third on is both oxygenated and reformulated. The upper Rhine valley is a very sensitive region for pollution episodes and several meteorological and air quality studies have already been performed. High temporal and spatial emission inventories are available allowing relevant and realistic modifications of the emission inventories. The calculation period, i.e., 11 May 1998, corresponds to a regional photochemical ozone pollution episode during which ozone concentrations exceeded several times the information threshold of the ozone directive of the European Union (180 µg m−3 as 1 hourly average). New emission inventories are set up using specific emission factors related to the alternative fuels by varying the fraction of gasoline passenger cars (from 50% to 100%) using the three fuel blends. Then air quality modeling simulations are performed using these emission inventories over the upper Rhine valley. The impact of alternative fuels on regional air quality is evaluated by comparing these simulations with the one using a reference emission inventory, e.g., where no modifications of the fuel composition are included. The results are analyzed by focusing on peak levels and daily averaged concentrations. The use of the alternative fuels leads to general reductions of ozone and volatile organic compounds (VOC) and increases of NOx levels. We found different behaviors related to the type of the area of concern i.e. rural or urban. The impacts on ozone are enhanced in urban areas where 15% reduction of the ozone peak and daily averaged concentrations can be reached. This behavior is similar for the NOx for which, in addition, an increase of the levels can be noted in urban plumes over rural areas. The most important decreases of the total VOC levels are mainly located over rural areas (more than 5% reduction of the levels except in urban plumes). By comparing these results with those from a local study related to the air quality of Strasbourg, we estimate that the regional contribution to the urban air quality of Strasbourg allows an enhancement of the results by using alternative fuel blends at the regional scale.
Uptake of hypobromous acid (HOBr) by aqueous sulfuric acid solutions: low-temperature solubility and reaction
Authors: Iraci L. T. , Michelsen R. R. , Ashbourn S. F. M. , Rammer T. A. , Golden D. M. 
Published: April 2010

Abstract. Hypobromous acid (HOBr) is a key species linking inorganic bromine to the chlorine and odd hydrogen chemical families. We have measured the solubility of HOBr in 45–70 wt% sulfuric acid solutions representative of upper tropospheric and lower stratospheric aerosol composition. Over the temperature range 201–252 K, HOBr is quite soluble in sulfuric acid, with an effective Henry's law coefficient, H*=104-107 mol L-1 atm-1. H* is inversely dependent on temperature, with ΔH=-45.0±5.4 kJ mol-1 and ΔS=-101±24 J mol-1 K-1 for 55–70 wt% H2SO4 solutions. Our study includes temperatures which overlap both previous measurements of HOBr solubility. For uptake into 55–70 wt% H2SO4, the solubility is described by log H*=(2349±280)/T–(5.27±1.24). At temperatures colder than ~213 K, the solubility of HOBr in 45 wt% H2SO4 is at least a factor of five larger than in 70 wt% H2SO4, with log H*=(3665±270)/T–(10.63±1.23). The solubility of HOBr is comparable to that of HBr, indicating that upper tropospheric and lower stratospheric aerosols should contain equilibrium concentrations of HOBr which equal or exceed those of HBr. Upon uptake of HOBr into aqueous sulfuric acid in the presence of other brominated gases, particularly for 70 wt% H2SO4 solution, our measurements demonstrate chemical reaction of HOBr followed by evolution of gaseous products including Br2O and Br2.
Naturally driven variability in the global secondary organic aerosol over a decade
Authors: Tsigaridis K. , Lathière J. , Kanakidou M. , Hauglustaine D. A. 
Published: April 2010

Abstract. In order to investigate the variability of the secondary organic aerosol (SOA) distributions and budget and provide a measure for the robustness of the conclusions on human induced changes of SOA, a global 3-dimensional chemistry transport model describing both the gas and the particulate phase chemistry of the troposphere has been applied. The response of the global budget of SOA to temperature and moisture changes as well as to biogenic emission changes over a decade (1984–1993) has been evaluated. The considered emissions of biogenic non-methane volatile organic compounds (VOC) are driven by temperature, light and vegetation. They vary between 756 and 810 TgC y-1 and are therefore about 5.5 times higher than the anthropogenic VOC emissions. All secondary aerosols (sulphuric, nitrates and organics) are computed on-line together with the aerosol associated water. Over the studied decade, the computed natural variations (8%) in the chemical SOA production from biogenic VOC oxidation equal the chemical SOA production from anthropogenic VOC oxidation. This computed variability results from a 7% increase in biogenic VOC emissions combined with 8.5% and 6% increases in the wet and dry deposition of SOA and leads to about 11.5% increase in the SOA burden of biogenic origin. The present study also demonstrates the importance of the hydrological cycle in determining the built up and fate of SOA in the atmosphere. It also reveals the existence of significant positive and negative feedback mechanisms in the atmosphere responsible for the non linear relationship between emissions of biogenic VOC and SOA burden.
Impact of the regional climate and substance properties on the fate and atmospheric long-range transport of persistent organic pollutants – examples of DDT and γ-HCH
Authors: Semeena V. S. , Feichter J. , Lammel G. 
Published: April 2010

Abstract. A global multicompartment model which is based on a 3-D atmospheric general circulation model (ECHAM5) coupled to 2-D soil, vegetation and sea surface mixed layer reservoirs, is used to simulate the atmospheric transports and total environmental fate of dichlorodiphenyltrichloroethane (DDT) and γ-hexachlorocyclohexane (γ-HCH, lindane). Emissions into the model world reflect the substance's agricultural usage in 1980 and 1990 and same amounts in sequential years are applied. Four scenarios of DDT usage and atmospheric decay and one scenario of γ-HCH are studied over a decade. The global environment is predicted to be contaminated by the substances within ca. 2 a (years). DDT reaches quasi-steady state within 3–4 a in the atmosphere and vegetation compartments, ca. 6 a in the sea surface mixed layer and near to or slightly more than 10 a in soil. Lindane reaches quasi-steady state in the atmosphere and vegetation within 2 a, in soils within 8 years and near to or slightly more than 10 a and in the sea surface mixed layer. The substances' differences in environmental behaviour translate into differences in the compartmental distribution and total environmental residence time, τoverall. τoverall≈0.8 a for γ-HCH's and ≈1.0–1.3 a for the various DDT scenarios. Both substances' distributions are predicted to migrate in northerly direction, 5–12° for DDT and 6.7° for lindane between the first and the tenth year in the environment. Cycling in various receptor regions is a complex superposition of influences of regional climate, advection, and the substance's physico-chemical properties. As a result of these processes the model simulations show that remote boreal regions are not necessarily less contaminated than tropical receptor regions. Although the atmosphere accounts for only 1% of the total contaminant burden, transport and transformation in the atmosphere is key for the distribution in other compartments. Hence, besides the physico-chemical properties of pollutants the location of application (entry) affects persistence and accumulation emphasizing the need for georeferenced exposure models.
Polar organic compounds in rural PM2.5 aerosols from K-puszta, Hungary, during a 2003 summer field campaign: sources and diurnal variations
Authors: Ion A. C. , Vermeylen R. , Kourtchev I. , Cafmeyer J. , Chi X. , Gelencsér A. , Maenhaut W. , Claeys M. 
Published: April 2010

Abstract. In the present study, we examined PM2.5 continental rural background aerosols, which were collected during a summer field campaign at K-puszta, Hungary (4 June–10 July 2003), a mixed coniferous/deciduous forest site characterized by intense solar radiation during summer. Emphasis was placed on polar oxygenated organic compounds that provide information on aerosol sources and source processes. Analysis was performed using gas chromatography/mass spectrometry (GC/MS) after suitable sample workup consisting of extraction with methanol and derivatisation into trimethylsilyl (TMS) derivatives. The major components detected at significant atmospheric concentrations were: (a) photo-oxidation products of isoprene including the 2-methyltetrols (2-methylthreitol and 2-methylerythritol) and 2-methylglyceric acid, (b) levoglucosan, a marker for biomass burning, (c) malic acid, an end-oxidation product of unsaturated fatty acids, and (d) the sugar alcohols, arabitol and mannitol, markers for fungal spores. Diurnal patterns with highest concentrations during day-time were observed for the isoprene oxidation products, i.e., the 2-methyltetrols and 2-methylglyceric acid, which can be regarded as supporting evidence for their fast photochemical formation from their locally emitted precursor. In addition, a diurnal pattern with highest concentrations during day-time was observed for the fungal markers, arabitol and mannitol, suggesting that the release of fungal fragments that are associated with the PM2.5 aerosol is enhanced during that time. Furthermore, a diurnal pattern was also found for levoglucosan with the highest concentrations at night when wood burning may take place in the settlements around the sampling site. In contrast, malic acid did not show day/night differences but was found to follow quite closely the particulate and organic carbon mass. This is interpreted as an indication that malic acid is formed in photochemical reactions which have a much longer overall time-scale than that of isoprene photo-oxidation, and the sources of its precursors are manifold, including both anthropogenic and natural emissions. On the basis of the high concentrations found for the isoprene oxidation products, i.e., the 2-methyltetrols (28.5 ng m-3) and 2-methylglyceric acid (7.6 ng m-3), it can be concluded that rapid photo-oxidation of isoprene is an important atmospheric chemistry process that contributes to secondary organic aerosol (SOA) formation at K-puszta during summer.
Alternative polarisation retrieval for SCIAMACHY in the ultraviolet
Authors: Tilstra L. G. , Stammes P. 
Published: April 2010

Abstract. We introduce an alternative method for the retrieval of polarisation in the ultraviolet by the satellite spectrometer SCIAMACHY. Unlike the operational polarisation retrieval algorithm, this method does not use the Polarisation Measurement Devices (PMDs) onboard SCIAMACHY, but only requires the reflectance signal. This makes the algorithm more robust and less sensitive to calibration errors caused by either improper characterisation of the instrument's response functions (key data) or degradation of the optical components. The alternative polarisation retrieval is able to retrieve the full state of atmospheric polarisation in the wavelength range between 330 and 400 nm, which is essentially the wavelength region covered by SCIAMACHY's PMD 1. This allows a direct comparison with the current operational product. When we compare the alternative polarisation algorithm with the operational algorithm, we find in some cases agreement, but not in other cases. The alternative algorithm compares well with an analytical model of the polarisation of a cloud-free scene. Using the alternative algorithm the polarisation-sensitive feature in the SCIAMACHY reflectance around 350 nm is automatically corrected for.
Airborne multi-axis DOAS measurements of tropospheric SO2 plumes in the Po-valley, Italy
Authors: Wang P. , Richter A. , Bruns M. , Burrows J. P. , Junkermann W. , Heue K.-P. , Wagner T. , Platt U. , Pundt I. 
Published: April 2010

Abstract. During the second FORMAT (FORMaldehyde as A Tracer of oxidation in the troposphere) campaign in 2003 the airborne multi-axis DOAS instrument (AMAXDOAS) performed spectroscopic measurements of SO2 from the city of Mantova and the power plant Porto Tolle using scattered sun-light during two flights on 26 and 27 September 2003. Measurements were performed in 10 different viewing directions, providing information on the vertical SO2 distribution and the SO2 vertical column. The SO2 emission flux from the power plant Porto Tolle was calculated to 1.6×1025 molec cm-2 (1.7 kg s-1) and was found to be the same on both measurement days, and also comparable to official emission data, which quote 2.25×1025 molec s-1 (26 September) and 2.07×1025 molec s-1 (27 September). Over the city of Mantova, the observed SO2 vertical columns were 1.1×1016 molec cm-2 and 1.9×1016 molec cm-2 on 26 and 27 September, respectively. This is in good agreement with ground-based measurements of 5.9 ppbv and 10.0 ppbv which correspond to 1.2×1016 molec cm-2 and 2.2×1016 molec cm-2.