bluuebunny/crossref_metadata_2025 huggingface dataset:
A look at aerosol formation using data mining techniques
Authors: Hyvönen S. , Junninen H. , Laakso L. , Dal Maso M. , Grönholm T. , Bonn B. , Keronen P. , Aalto P. , Hiltunen V. , Pohja T. , Launiainen S. , Hari P. , Mannila H. , Kulmala M.
Published: April 2010

Abstract. Atmospheric aerosol particle formation is frequently observed throughout the atmosphere, but despite various attempts of explanation, the processes behind it remain unclear. In this study data mining techniques were used to find the key parameters needed for atmospheric aerosol particle formation to occur. A dataset of 8 years of 80 variables collected at the boreal forest station (SMEAR II) in Southern Finland was used, incorporating variables such as radiation, humidity, SO2, ozone and present aerosol surface area. Data analysis were done using clustering and classification methods. The aim of this approach was to gain new parameters independent of any subjective interpretation. This resulted in two key parameters, relative humidity and preexisting aerosol particle surface (condensation sink), capable in explaining 88% of the nucleation events. The inclusion of any further parameters did not improve the results notably. Using these two variables it was possible to derive a nucleation probability function. Interestingly, the two most important variables are related to mechanisms that prevent the nucleation from starting and particles from growing, while parameters related to initiation of particle formation seemed to be less important. Nucleation occurs only with low relative humidity and condensation sink values. One possible explanation for the effect of high water content is that it prevents biogenic hydrocarbon ozonolysis reactions from producing sufficient amounts of low volatility compounds, which might be able to nucleate. Unfortunately the most important biogenic hydrocarbon compound emissions were not available for this study. Another effect of water vapour may be due to its linkage to cloudiness which may prevent the formation of nucleating and/or condensing vapours. A high number of preexisting particles will act as a sink for condensable vapours that otherwise would have been able to form sufficient supersaturation and initiate the nucleation process.
The thermal and dynamical state of the atmosphere during polar mesosphere winter echoes
Authors: Lübken F.-J. , Strelnikov B. , Rapp M. , Singer W. , Latteck R. , Brattli A. , Hoppe U.-P. , Friedrich M.
Published: April 2010

Abstract. In January 2005, a total of 18 rockets were launched from the Andøya Rocket Range in Northern Norway (69° N) into strong VHF radar echoes called 'Polar Mesosphere Winter Echoes' (PMWE). The echoes were observed in the lower and middle mesosphere during large solar proton fluxes. In general, PMWE are much more seldom compared to their summer counterparts PMSE (typical occurrence rates at 69° N are 1–3% vs. 80%, respectively). Our in-situ measurements by falling sphere, chaff, and instrumented payloads provide detailed information about the thermal and dynamical state of the atmosphere and therefore allow an unprecedented study of the background atmosphere during PMWE. There are a number of independent observations indicating that neutral air turbulence has caused PMWE. Ion density fluctuations show a turbulence spectrum within PMWE and no fluctuations outside. Temperature lapse rates close to the adiabatic gradient are observed in the vicinity of PMWE indicating persistent turbulent mixing. The spectral broadening of radar echoes is consistent with turbulent velocity fluctuations. Turbulence also explains the mean occurrence height of PMWE (~68–75 km): Viscosity increases rapidly with altitude and destroys any small scale fluctuations in the upper mesosphere, whereas electron densities are usually too low in the lower mesosphere to cause significant backscatter. The seasonal variation of echoes in the lower mesosphere is in agreement with a turbulence climatology derived from earlier sounding rocket flights. We have performed model calculations to study the absolute magnitude of backscatter from plasma fluctuations caused by neutral air turbulence. We find that volume reflectivities observed during PMWE are in quantitative agreement with theory. Apart from turbulence the most crucial requirement for PMWE is a sufficiently large number of electrons, for example produced by solar protons. We have studied the sensitivity of the radar echo strength on various parameters, most important electron number density and turbulence intensity. Our observational and theoretical considerations do not provide any evidence that charged aerosol particles are needed to explain PMWE, in contrast to the summer echoes which owe their existence to charged ice particles.
Simulating the detailed chemical composition of secondary organic aerosol formed on a regional scale during the TORCH 2003 campaign in the southern UK
Authors: Johnson D. , Utembe S. R. , Jenkin M. E.
Published: April 2010

Abstract. Following on from the companion study (Johnson et al., 2005a), a photochemical trajectory model (PTM) has been used to simulate the chemical composition of organic aerosol for selected events during the 2003 TORCH (Tropospheric Organic Chemistry Experiment) field campaign. The PTM incorporates the speciated emissions of 124 non-methane anthropogenic volatile organic compounds (VOC) and three representative biogenic VOC, a highly-detailed representation of the atmospheric degradation of these VOC, the emission of primary organic aerosol (POA) material and the formation of secondary organic aerosol (SOA) material. SOA formation was represented by the transfer of semi- and non-volatile oxidation products from the gas-phase to a condensed organic aerosol-phase, according to estimated thermodynamic equilibrium phase-partitioning characteristics for around 2000 reaction products. After significantly scaling all phase-partitioning coefficients, and assuming a persistent background organic aerosol (both required in order to match the observed organic aerosol loadings), the detailed chemical composition of the simulated SOA has been investigated in terms of intermediate oxygenated species in the Master Chemical Mechanism, version 3.1 (MCM v3.1). For the various case studies considered, 90% of the simulated SOA mass comprises between ca. 70 and 100 multifunctional oxygenated species derived, in varying amounts, from the photooxidation of VOC of anthropogenic and biogenic origin. The anthropogenic contribution is dominated by aromatic hydrocarbons and the biogenic contribution by α- and β-pinene (which also constitute surrogates for other emitted monoterpene species). Sensitivity in the simulated mass of SOA to changes in the emission rates of anthropogenic and biogenic VOC has also been investigated for 11 case study events, and the results have been compared to the detailed chemical composition data. The role of accretion chemistry in SOA formation, and its implications for the results of the present investigation, is discussed.
Meteorology applied to urban air pollution problems: concepts from COST 715
Authors: Fisher P. , Kukkonen J. , Piringer M. , Rotach M. W. , Schatzmann M.
Published: April 2010

Abstract. This selective review of the COST 715 considers simple descriptive concepts in urban meteorology with particular attention to air pollution assessment. It is shown that these are helpful for understanding the complex structure of the urban boundary layer, but that simple concepts only apply under a limited number of occasions. However such concepts are necessary for insight into how both simple and complex air pollution models perform. Wider considerations are needed when considering routine air quality assessments involving an air quality model's formulation and pedigree. It is argued that there is a reluctance from model developers to move away from familiar concepts of the atmospheric boundary layer even if they are not appropriate to urban areas. An example is given from COST 715 as to how routine urban meteorological measurements of wind speed may be used and adapted for air quality assessments. Reference to the full COST 715 study is made which provides further details.
Simulating aerosol microphysics with the ECHAM/MADE GCM – Part I: Model description and comparison with observations
Authors: Lauer A. , Hendricks J. , Ackermann I. , Schell B. , Hass H. , Metzger S.
Published: April 2010

Abstract. The aerosol dynamics module MADE has been coupled to the general circulation model ECHAM4 to simulate the chemical composition, number concentration, and size distribution of the global submicrometer aerosol. The present publication describes the new model system ECHAM4/MADE and presents model results in comparison with observations. The new model is able to simulate the full life cycle of particulate matter and various gaseous precursors including emissions of primary particles and trace gases, advection, convection, diffusion, coagulation, condensation, nucleation of sulfuric acid vapor, aerosol chemistry, cloud processing, and size-dependent dry and wet deposition. Aerosol components considered are sulfate (SO4), ammonium (NH4), nitrate (NO3), black carbon (BC), particulate organic matter (POM), sea salt, mineral dust, and aerosol liquid water. The model is numerically efficient enough to allow long term simulations, which is an essential requirement for application in general circulation models. In order to evaluate the results obtained with this new model system, calculated mass concentrations, particle number concentrations, and size distributions are compared to observations. The intercomparison shows, that ECHAM4/MADE is able to reproduce the major features of the geographical patterns, seasonal cycle, and vertical distributions of the basic aerosol parameters. In particular, the model performs well under polluted continental conditions in the northern hemispheric lower and middle troposphere. However, in comparatively clean remote areas, e.g. in the upper troposphere or in the southern hemispheric marine boundary layer, the current model version tends to underestimate particle number concentrations.
Single particle analysis of ice crystal residuals observed in orographic wave clouds over Scandinavia during INTACC experiment
Authors: Targino A. C. , Krejci R. , Noone K. J. , Glantz P.
Published: April 2010

Abstract. Individual ice crystal residual particles collected over Scandinavia during the INTACC (INTeraction of Aerosol and Cold Clouds) experiment in October 1999 were analyzed by Scanning Electron Microscopy (SEM) equipped with Energy-Dispersive X-ray Analysis (EDX). Samples were collected onboard the British Met Office Hercules C-130 aircraft using a Counterflow Virtual Impactor (CVI). This study is based on six samples collected in orographic clouds. The main aim of this study is to characterize cloud residual elemental composition in conditions affected by different airmasses. In total 609 particles larger than 0.1 µm diameter were analyzed and their elemental composition and morphology were determined. Thereafter a hierarchical cluster analysis was performed on the signal detected with SEM-EDX in order to identify the major particle classes and their abundance. A cluster containing mineral dust, represented by aluminosilicates, Fe-rich and Si-rich particles, was the dominating class of particles, accounting for about 57.5% of the particles analyzed, followed by low-Z particles, 23.3% (presumably organic material) and sea salt (6.7%). Sulfur was detected often across all groups, indicating ageing and in-cloud processing of particles. A detailed inspection of samples individually unveiled a relationship between ice crystal residual composition and airmass origin. Cloud residual samples from clean airmasses (that is, trajectories confined to the Atlantic and Arctic Oceans and/or with source altitude in the free troposphere) were dominated primarily by low-Z and sea salt particles, while continentally-influenced airmasses (with trajectories that originated or traveled over continental areas and with source altitude in the continental boundary layer) contained mainly mineral dust residuals. Comparison of residual composition for similar cloud ambient temperatures around −27°C revealed that supercooled clouds are more likely to persist in conditions where low-Z particles represent significant part of the analyzed cloud residual particles. This indicates that organic material inhibits freezing, in contrast to polluted cases when ice crystal formation was observed at the same conditions and when the cloud residual composition was dominated by mineral dust. The presented results suggest that the chemical composition of cloud nuclei and airmass origin have a strong impact on the ice formation through heterogeneous freezing in supercooled clouds.
Size distribution and hygroscopic properties of aerosol particles from dry-season biomass burning in Amazonia
Authors: Rissler J. , Vestin A. , Swietlicki E. , Fisch G. , Zhou J. , Artaxo P. , Andreae M. O.
Published: April 2010

Abstract. Aerosol particle number size distributions and hygroscopic properties were measured at a pasture site in the southwestern Amazon region (Rondonia). The measurements were performed 11 September–14 November 2002 as part of LBA-SMOCC (Large scale Biosphere atmosphere experiment in Amazonia – SMOke aerosols, Clouds, rainfall and Climate), and cover the later part of the dry season (with heavy biomass burning), a transition period, and the onset of the wet period. Particle number size distributions were measured with a DMPS (Differential Mobility Particle Sizer, 3–850 nm) and an APS (Aerodynamic Particle Sizer), extending the distributions up to 3.3 µm in diameter. An H-TDMA (Hygroscopic Tandem Differential Mobility Analyzer) measured the hygroscopic diameter growth factors (Gf) at 90% relative humidity (RH), for particles with dry diameters (dp) between 20–440 nm, and at several occasions RH scans (30–90% RH) were performed for 165 nm particles. These data provide the most extensive characterization of Amazonian biomass burning aerosol, with respect to particle number size distributions and hygroscopic properties, presented until now. The evolution of the convective boundary layer over the course of the day causes a distinct diel variation in the aerosol physical properties, which was used to get information about the properties of the aerosol at higher altitudes. The number size distributions averaged over the three time periods showed three modes; a nucleation mode with count median diameters (CMD) of ~12 nm, an Aitken mode (CMD = 61–92 nm) and an accumulation mode (CMD = 128–190 nm). The two larger modes were shifted towards larger CMD with increasing influence from biomass burning.
Distinction between clouds and ice/snow covered surfaces in the identification of cloud-free observations using SCIAMACHY PMDs
Authors: Krijger J. M. , Aben I. , Schrijver H.
Published: April 2010

Abstract. SCIAMACHY on ENVISAT allows measurement of different trace gases including those most abundant in the troposphere (e.g. CO2, NO2, CH4). However, clouds in the observed scenes can severely hinder the observation of tropospheric gases. Several cloud detection algorithms have been developed for GOME on ERS-2 which can be applied to SCIAMACHY. The GOME cloud algorithms, however, suffer from the inadequacy of not being able to distinguish between clouds and ice/snow covered surfaces because GOME only covers the UV, VIS and part of the NIR wavelength range (240–790 nm). As a result these areas are always flagged as clouded, and therefore often not used. Here a method is presented which uses the SCIAMACHY measurements in the wavelength range between 450 nm and 1.6 µm to make a distinction between clouds and ice/snow covered surfaces. The algorithm is developed using collocated MODIS observations. The algorithm presented here is specifically developed to identify cloud-free SCIAMACHY observations. The SCIAMACHY Polarisation Measurement Devices (PMDs) are used for this purpose because they provide higher spatial resolution compared to the main spectrometer measurements.
An AeroCom initial assessment – optical properties in aerosol component modules of global models
Authors: Kinne S. , Schulz M. , Textor C. , Guibert S. , Balkanski Y. , Bauer S. E. , Berntsen T. , Berglen T. F. , Boucher O. , Chin M. , Collins W. , Dentener F. , Diehl T. , Easter R. , Feichter J. , Fillmore D. , Ghan S. , Ginoux P. , Gong S. , Grini A. , Hendricks J. , Herzog M. , Horowitz L. , Isaksen I. , Iversen T. , Kirkevåg A. , Kloster S. , Koch D. , Kristjansson J. E. , Krol M. , Lauer A. , Lamarque J. F. , Lesins G. , Liu X. , Lohmann U. , Montanaro V. , Myhre G. , Penner J. , Pitari G. , Reddy S. , Seland O. , Stier P. , Takemura T. , Tie X.
Published: April 2010

Abstract. The AeroCom exercise diagnoses multi-component aerosol modules in global modeling. In an initial assessment simulated global distributions for mass and mid-visible aerosol optical thickness (aot) were compared among 20 different modules. Model diversity was also explored in the context of previous comparisons. For the component combined aot general agreement has improved for the annual global mean. At 0.11 to 0.14, simulated aot values are at the lower end of global averages suggested by remote sensing from ground (AERONET ca. 0.135) and space (satellite composite ca. 0.15). More detailed comparisons, however, reveal that larger differences in regional distribution and significant differences in compositional mixture remain. Of particular concern are large model diversities for contributions by dust and carbonaceous aerosol, because they lead to significant uncertainty in aerosol absorption (aab). Since aot and aab, both, influence the aerosol impact on the radiative energy-balance, the aerosol (direct) forcing uncertainty in modeling is larger than differences in aot might suggest. New diagnostic approaches are proposed to trace model differences in terms of aerosol processing and transport: These include the prescription of common input (e.g. amount, size and injection of aerosol component emissions) and the use of observational capabilities from ground (e.g. measurements networks) or space (e.g. correlations between aerosol and clouds).
Measurements of CO2, its stable isotopes, O2/N2, and 222Rn at Bern, Switzerland
Authors: Sturm P. , Leuenberger M. , Valentino F. L. , Lehmann B. , Ihly B.
Published: April 2010

Abstract. A one-year time series of continuous atmospheric CO2 measurements from Bern, Switzerland is presented. O2/N2 and Ar/N2 ratios as well as stable carbon and oxygen isotopes of CO2 and δ29N2, δ34O2 and δ36Ar were measured periodically in a continuous way during a one year period. Additionally, the 222Rn activity was measured during three months in the winter 2004. Using the correlation from short term fluctuations of CO2 and 222Rn we estimated a mean CO2 flux density between February 2004 and April 2004 in the region of Bern of 95±39 tC km−2 month−1. The continuous observations of carbon dioxide and associated tracers shed light on diurnal and seasonal patterns of the carbon cycle in an urban atmosphere. There is considerable variance in nighttime δ13C and δ18O of source CO2 throughout the year, however, with generally lower values in winter compared to summertime. The O2:CO2 oxidation ratio during the nighttime build-up of CO2 varies between −0.96 and −1.69 mol O2/mol CO2. Furthermore, Ar/N2 measurements showed that artifacts like thermal fractionation at the air intake are relevant for high precision measurements of atmospheric O2.
Measurements of NO, NOy, N2O, and O3 during SPURT: implications for transport and chemistry in the lowermost stratosphere
Authors: Hegglin M. I. , Brunner D. , Peter Th. , Hoor P. , Fischer H. , Staehelin J. , Krebsbach M. , Schiller C. , Parchatka U. , Weers U.
Published: April 2010

Abstract. We present measurements of NO, NOy, O3, and N2O within the lowermost stratosphere (LMS) over Europe obtained during the SPURT project. The measurements cover each of the four seasons during two years between November 2001 and July 2003, and probe the entire altitude and latitude range of the LMS: from 5° N to 85° N equivalent latitude, and from 290 to 375 K potential temperature. The measurements represent a comprehensive data set of these tracers and reveal atmospheric transport processes that influence tracer distributions in the LMS. Mean mixing ratios of stratospheric tracers in equivalent latitude-potential temperature coordinates show a clear seasonal cycle related to the Brewer-Dobson circulation with highest values in spring and lowest values in autumn. Vertical profiles show strong gradients at the extratropical tropopause suggesting that vertical (cross-isentropic) mixing is reduced above the tropopause. Mixing along isentropes is also strongly reduced since pronounced meridional gradients are found on potential temperature surfaces in the LMS. Concurrent large gradients in PV in the vertical and in the meridional direction horizontally suggest the presence of a transport and mixing barrier. Well above the tropopause distinguished seasonal cycles were found in the correlation slopes ΔO3/ΔN2O and ΔNOy/ΔN2O. Smallest slopes found during spring indicate chemically aged stratospheric air originating from high altitudes and latitudes. The slopes are larger in summer and autumn suggesting that a substantial fraction of air takes a 'short-cut' from the tropical tropopause region into the extratropical LMS. The comparison of measured NO with critical NO values at which net ozone production changes from negative to positive implies a net ozone production up to 20 K above the local tropopause in winter, increasing during spring and summer to up to 50 K in autumn. Above this height NO values favor ozone destruction.
Technical Note: Simulating chemical systems in Fortran90 and Matlab with the Kinetic PreProcessor KPP-2.1
Authors: Sandu A. , Sander R.
Published: April 2010

Abstract. This paper presents the new version 2.1 of the Kinetic PreProcessor (KPP). Taking a set of chemical reactions and their rate coefficients as input, KPP generates Fortran90, Fortran77, Matlab, or C code for the temporal integration of the kinetic system. Efficiency is obtained by carefully exploiting the sparsity structures of the Jacobian and of the Hessian. A comprehensive suite of stiff numerical integrators is also provided. Moreover, KPP can be used to generate the tangent linear model, as well as the continuous and discrete adjoint models of the chemical system.
Sensitivity analysis by the adjoint chemistry transport model DRAIS for an episode in the Berlin ozone (BERLIOZ) experiment
Authors: Nester K. , Panitz H.-J.
Published: April 2010

Abstract. The Berlin Ozone Experiment (BERLIOZ) was carried out in summer 1998. One of its purposes was the evaluation of Chemistry Transport Models (CTM). CTM KAMM/DRAIS was one of the models considered. The data of 20 July were selected for evaluation. On that day, a pronounced ozone plume developed downwind of the city. Evaluation showed that the KAMM/DRAIS model is able to reproduce the meteorological and ozone data observed, except at distances far downwind of the city (60–80 km). In that region, the DRAIS model underestimates the measured ozone concentrations by approx. (10–15) ppb. Therefore, this study was conducted to detect possible reasons for this deviation. A comprehensive sensitivity analysis was carried out, to determine the most relevant model parameters. The adjoint DRAIS model was developed for this purpose, because the most effective method of calculating the sensitivities is the application of the adjoint model. The least squares of the measured and simulated ozone concentrations between 08.0 UTC and 16.0 UTC at two stations 30 km and 70 km downwind of the city centre were chosen as the distance function. The model parameters considered in this study are the complete set of initial and boundary species concentrations, emissions, and reaction rates, respectively. A sensitivity ranking showing the relevance of the individual parameters in the set is determined for each parameter set. In order to find out which modification in the parameter sets most reduces the distance function, simplified 4-D data assimilation was carried out. The result of this data assimilation shows that modifications of the reaction rates provide the best agreement between the measured and the simulated ozone concentrations at both stations. However, agreement is still acceptable when the parameters in the other sets are modified together. The investigation demonstrates that an analysis of this type can help to explain inconsistencies between observations and simulations. The analysis also shows, however, that the parameters responsible cannot be determined unequivocally.
Size and composition measurements of background aerosol and new particle growth in a Finnish forest during QUEST 2 using an Aerodyne Aerosol Mass Spectrometer
Authors: Allan J. D. , Alfarra M. R. , Bower K. N. , Coe H. , Jayne J. T. , Worsnop D. R. , Aalto P. P. , Kulmala M. , Hyötyläinen T. , Cavalli F. , Laaksonen A.
Published: April 2010

Abstract. The study of the growth of nucleation-mode particles is important, as this prevents their loss through diffusion and allows them to reach sizes where they may become effective cloud condensation nuclei. Hyytiälä, a forested site in southern Finland, frequently experiences particle nucleation events during the spring and autumn, where particles first appear during the morning and continue to grow for several hours afterwards. As part of the QUEST 2 intensive field campaign during March and April 2003, an Aerodyne Aerosol Mass Spectrometer (AMS) was deployed alongside other aerosol instrumentation to study the particulate composition and dynamics of growth events and characterise the background aerosol. Despite the small mass concentrations, the AMS was able to distinguish the grown particles in the <100 nm regime several hours after an event and confirm that the particles were principally organic in composition. The AMS was also able to derive a mass spectral fingerprint for the organic species present, and found that it was consistent between events and independent of the mean particle diameter during non-polluted cases, implying the same species were also condensing onto the accumulation mode. The results were compared with those from offline analyses such as GC-MS and were consistent with the hypothesis that the main components were alkanes from plant waxes and the oxidation products of terpenes.
Transport and chemical transformations influenced by shallow cumulus over land
Authors: Vilà-Guerau de Arellano J. , Kim S.-W. , Barth M. C. , Patton E. G.
Published: April 2010

Abstract. The distribution and evolution of reactive species in a boundary layer characterized by the presence of shallow cumulus over land is studied by means of two large-eddy simulation models: the NCAR and WUR codes. The study focuses on two physical processes that can influence the chemistry: the enhancement of the vertical transport by the buoyant convection associated with cloud formation and the perturbation of the photolysis rates below, in and above the clouds. It is shown that the dilution of the reactant mixing ratio caused by the deepening of the atmospheric boundary layer is an important process and that it can decrease reactant mixing ratios by 10 to 50 percent compared to very similar conditions but with no cloud formation. Additionally, clouds transport chemical species to higher elevations in the boundary layer compared to the case with no clouds which influences the reactant mixing ratios of the nocturnal residual layers following the collapse of the daytime boundary layer. Estimates of the rate of reactant transport based on the calculation of the integrated flux divergence range from to −0.2 ppb hr−1 to −1 ppb hr−1, indicating a net loss of sub-cloud layer air transported into the cloud layer. A comparison of this flux to a parameterized mass flux shows good agreement in mid-cloud, but at cloud base the parameterization underestimates the mass flux. Scattering of radiation by cloud drops perturbs photolysis rates. It is found that these perturbed photolysis rates substantially (10–40%) affect mixing ratios locally (spatially and temporally), but have little effect on mixing ratios averaged over space and time. We find that the ultraviolet radiance perturbation becomes more important for chemical transformations that react with a similar order time scale as the turbulent transport in clouds. Finally, the detailed intercomparison of the LES results shows very good agreement between the two codes when considering the evolution of the reactant mean, flux and (co-)variance vertical profiles.
SCIAMACHY Level1 data: Calibration concept and in-flight calibration
Authors: Lichtenberg G. , Kleipool Q. , Krijger J. M. , van Soest G. , van Hees R. , Tilstra L. G. , Acarreta J. R. , Aben I. , Ahlers B. , Bovensmann H. , Chance K. , Gloudemans A. M. S. , Hoogeveen R. W. M. , Jongma R. , Noël S. , Piters A. , Schrijver H. , Schrijvers C. , Sioris C. E. , Skupin J. , Slijkhuis S. , Stammes P. , Wuttke M.
Published: April 2010

Abstract. This paper discusses the basic concept of the calibration of the SCIAMACHY instrument and remaining open issues. SCIAMACHY is a scanning Limb/Nadir spectrometer covering the wavelength range from 212 nm to 2386 nm. It was launched on-board ENVISAT in February 2002. In general the instrument performance is excellent: It performs as tested on ground and there is only very minor degradation in time. The only exception is the unexpected formation of water ice on the infrared channels 7 and 8 that attenuates the signal and a light leak in channel 7. Both effects will be discussed. In the paper we will explain all individual calibration steps needed to come to a wavelength calibrated spectrum of the Earth reflectance. Open points in the calibrations and latest improvements, such as the new radiometric calibration will also be treated.
The effect of systematic measurement errors on atmospheric CO2 inversions: a quantitative assessment
Authors: Rödenbeck C. , Conway T. J. , Langenfelds R.
Published: April 2010

Abstract. Surface-atmosphere exchange fluxes of CO2, estimated by an interannual atmospheric transport inversion from atmospheric mixing ratio measurements, are affected by several sources of errors, one of which is experimental errors. Quantitative information about such measurement errors can be obtained from regular co-located measurements done by different laboratories or using different experimental techniques. The present quantitative assessment is based on intercomparison information from the CMDL and CSIRO atmospheric measurement programs. We show that the effects of systematic measurement errors on inversion results are very small compared to other errors in the flux estimation (as well as compared to signal variability). As a practical consequence, this assessment justifies the merging of data sets from different laboratories or different experimental techniques (flask and in-situ), if systematic differences (and their changes) are comparable to those considered here. This work also highlights the importance of regular intercomparison programs.
Modelling study of the impact of deep convection on the UTLS air composition – Part II: Ozone budget in the TTL avenue de la Recherche Scientifique, 45071 Orléans cedex 2, France
Authors: Rivière E. D. , Marécal V. , Larsen N. , Cautenet S.
Published: April 2010

Abstract. In this second part of a series of two papers which aim to study the local impact of deep convection on the chemical composition of the Upper Troposphere and Lower Stratosphere (UTLS), we focus on ozone simulation results using a mesoscale model that includes on-line chemistry. A severe convective system observed on 8 February 2001 at Bauru, Brazil, is studied. We show that there is an increase in the ozone concentration in the tropical transitional layer (TTL) in the model during this event, which is compatible with ozone sonde observations from Bauru during the 2004 convective season. The model horizontal variability of ozone in this layer is comparable with the variability of the ozone sonde observations in the same area. The calculation of the ozone budget in the TTL shows that the ozone behaviour in this layer is mainly driven by dynamics. The upward motions at the bottom of the TTL, related to the convection activity is the main contributor to the budget since it can explain 75% of the total ozone increase in the TTL, while the chemical ozone production inside the TTL is estimated to be 23.5% of the ozone increase if NOx production by lightning (LNOx) is taken into account. It is shown that downward motions at the tropopause induced by gravity waves generated by deep convection are non negligible in the TTL ozone budget, since it represents 11% of the ozone increase. The correlation between the convection activity and the vertical flux at 13 km, the vertical flux at 17 km, and the chemical production is brought to the fore in this simulation.
Sensitivity studies on the photolysis rates calculation in Amazonian atmospheric chemistry – Part I: The impact of the direct radiative effect of biomass burning aerosol particles
Authors: Albuquerque L. M. M. , Longo K. M. , Freitas S. R. , Tarasova T. , Plana Fattori A. , Nobre C. , Gatti L. V.
Published: April 2010

Abstract. The impact of the direct radiative effect of the aerosol particles on the calculation of the photolysis rates and consequently on the atmospheric chemistry in regional smoke clouds due to biomass burning over the Amazon basin is addressed in this work. It explores a case study for 19 September 2002 at LBA-RACCI-SMOCC (The Large-Scale Biosphere-Atmosphere experiment in Amazonia – Radiation, Cloud, and Climate Interactions – Smoke, Aerosols, Clouds, Rainfall and Climate) pasture site in SW Amazonia. The Tropospheric Ultraviolet Visible radiation model (TUV) version 4.2, (Madronich et al., 1987) is used for the photolysis rates calculation considering the layer aerosol optical depth from the Coupled Aerosol Tracer Transport model to the Brazilian Regional Atmospheric Modeling System (CATT-BRAMS) (Freitas et al., 2005). A dynamical aerosol model (Procópio et al., 2003) is included in the radiative transfer model to take into account the high temporal variability of the aerosol optical thickness. This methodology is tested by comparing modeled and measured clear sky solar irradiances. The results show a good agreement with measured PAR radiation values. The actinic flux attenuation, for AOT (500 nm) values around 1.94, decreases the photolysis rates by about 70% in the presence of near-ground smoke aerosol and above the smoke layer the photolysis process tends to increase by about 40%. A simulation of the ozone production is carried out using a one-dimensional photochemical box model and comparisons with observation are shown.
Sensitivity analysis of methane emissions derived from SCIAMACHY observations through inverse modelling
Authors: Meirink J. F. , Eskes H. J. , Goede A. P. H.
Published: April 2010

Abstract. Satellite observations of trace gases in the atmosphere offer a promising method for global verification of emissions and improvement of global emission inventories. Here, an inverse modelling approach based on four-dimensional variational (4D-var) data assimilation is presented and applied to synthetic measurements of atmospheric methane. In this approach emissions and initial concentrations are optimised simultaneously, thus allowing inversions to be carried out on time scales of weeks to months, short compared with the lifetime of methane. Observing System Simulation Experiments (OSSEs) have been performed to demonstrate the feasibility of the method and to investigate the utility of SCIAMACHY observations for methane source estimation. The impact of a number of parameters on the error in the methane emission field retrieved has been analysed. These parameters include the measurement error, the error introduced by the presence of clouds, and the spatial resolution of the emission field. It is shown that 4D-var is an efficient method to deal with large amounts of satellite data and to retrieve emissions at high resolution. Some important conclusions regarding the SCIAMACHY measurements can be drawn: (i) the observations at their estimated precision of 1.5 to 2% will contribute considerably to uncertainty reduction in monthly, subcontinental (~500 km) methane source strengths; (ii) it is essential to take partly cloudy pixels into account in order to achieve sufficient spatial coverage; and (iii) the uncertainty in measured cloud parameters may at some point become the limiting factor, rather than the uncertainty in measured methane.
Water vapour profiles by ground-based FTIR spectroscopy: study for an optimised retrieval and its validation
Authors: Schneider M. , Hase F. , Blumenstock T.
Published: April 2010

Abstract. The sensitivity of ground-based instruments measuring in the infrared with respect to tropospheric water vapour content is generally limited to the lower and middle troposphere. The large vertical gradients and variabilities avoid a better sensitivity for the upper troposphere/lower stratosphere region. In this work an optimised retrieval is presented and it is demonstrated that compared to a commonly applied method, it widely improves the performance of the FTIR technique with respect to upper tropospheric water vapour. Within a realistic error scenario it is estimated that the optimised method reduces the upper tropospheric uncertainties by about 25–30%, leading to a noise to signal ratio of 50%. The reasons for this improvement and the possible deficiencies of the method are discussed. The estimations are confirmed by a comparison of retrieval results based on real FTIR measurements with coinciding measurements of synoptical meteorological radiosondes.
The origin of ozone
Authors: Grewe V.
Published: April 2010

Abstract. Highest ozone production rates can be found at around 30 km in the tropical stratosphere, leading to ozone mixing ratios of about 10 ppmv. Those stratospheric air masses are then transported to extra-tropical latitudes via the Brewer-Dobson Circulation. This is thought to be the main mechanism, how mid- and high latitude ozone is generated. By applying the climate-chemistry model E39/C, this view is investigated in more detail. The origin of ozone in the troposphere and stratosphere is analyzed, by incorporating a diagnostic (''marked ozone origin tracers'') into the model, which allows to identify the origin of ozone. In most regions the local simulated ozone concentration is dominated by local ozone production, i.e. less than 50% of the ozone at higher stratospheric latitudes is produced in the tropics, which conflicts with the idea that the tropics are the global source for stratospheric ozone. Although episodic stratospheric intrusions occur basically everywhere, the main ozone stratosphere-to-troposphere exchange is connected to exchange processes at the sub-tropical jet-stream. The tropospheric influx of ozone amounts to 420 Tg per year, and originates on the Northern Hemisphere from the extra-tropical stratosphere, whereas on the Southern Hemisphere a re-circulation of tropical tropospheric ozone contributes most to the influx of ozone into the troposphere. In the model, the upper tropopause of both hemispherers is clearly dominated by tropical tropospheric ozone (40%–50%) except for Northern Summer, where the tropospheric contribution (from the tropics as well as from the Northern Hemisphere) does not exceed 20%.
Atmospheric HULIS: how humic-like are they? A comprehensive and critical review
Authors: Graber E. R. , Rudich Y.
Published: April 2010

Abstract. A class of organic molecules extracted from atmospheric aerosol particles and isolated from fog and cloud water has been termed humic-like substances (HULIS) due to certain resemblance to terrestrial and aquatic humic and fulvic acids. In light of the interest that this class of atmospheric compounds currently attracts, we comprehensively review HULIS properties, as well as laboratory and field investigations concerning their formation and characterization in atmospheric samples. While sharing some basic features, accumulating evidence suggests that atmospheric HULIS differ substantially from terrestrial and aquatic humic substances. Major differences between HULIS and humic substances, including smaller average molecular weight, lower aromatic moiety content and higher aliphatic moiety and polysaccharide contents, as well as others, are highlighted. Several alternatives are proposed that may explain such differences: (1) the possibility that mono- and di-carboxylic acids and mineral acids abundant in the atmosphere prevent the formation of large humic ''supramolecular associations''; (2) that large humic macromolecules are destroyed in the atmosphere by UV radiation, O3, and OH-radicals; (3) that ''HULIS'' actually consists of a complex, unresolved mixture of relatively small molecules rather than macromolecular entities; and (4) that HULIS formed via abiotic and short-lived oxidative reaction pathways differs substantially from humic substances formed over long time periods via biologically-mediated reactions. It is concluded that a significant effort towards adopting standard extraction and characterization methods is required to develop a better and more meaningful comparison between different HULIS samples. The essential differences as denoted throughout, point to the possibility that HULIS may not be nearly as humic-like as hitherto believed.
Ozone observations by the Gas and Aerosol Measurement Sensor during SOLVE II
Authors: Pitts M. C. , Thomason L. W. , Zawodny J. M. , Wenny B. N. , Livingston J. M. , Russell P. B. , Yee J.-H. , Swartz W. H. , Shetter R. E.
Published: April 2010

Abstract. The Gas and Aerosol Measurement Sensor (GAMS) was deployed aboard the NASA DC-8 aircraft during the second SAGE III Ozone Loss and Validation Experiment (SOLVE II). GAMS acquired line-of-sight (LOS) direct solar irradiance spectra during the sunlit portions of ten science flights of the DC-8 between 12 January and 4 February 2003. Differential line-of-sight (DLOS) optical depth spectra are produced from the GAMS raw solar irradiance spectra. Then, DLOS ozone number densities are retrieved from the GAMS spectra using a multiple linear regression spectral fitting technique. Both the DLOS optical depth spectra and retrieved ozone data are compared with coincident measurements from two other solar instruments aboard the DC-8 platform to demonstrate the robustness and stability of the GAMS data. The GAMS ozone measurements are then utilized to evaluate the quality of the Wulf band ozone cross sections, a critical component of the SAGE III aerosol, water vapor, and temperature/pressure retrievals. Results suggest the ozone cross section compilation of Shettle and Anderson currently used operationally in SAGE III data processing may be in error by as much as 10–20% in the Wulf bands, and their lack of reported temperature dependence is a significant deficiency. A second, more recent, cross section database compiled for the SCIAMACHY satellite mission appears to be of much better quality in the Wulf bands, but still may have errors as large as 5% near the Wulf band absorption peaks. Additional laboratory measurements of the Wulf band cross sections should be pursued to further reduce their uncertainty and better quantify their temperature dependence.
Observation of unusual chlorine activation by ground-based infrared and microwave spectroscopy in the late Arctic winter 2000/01
Authors: Blumenstock T. , Kopp G. , Hase F. , Hochschild G. , Mikuteit S. , Raffalski U. , Ruhnke R.
Published: April 2010

Abstract. During the Arctic winter of 2000/01, ground-based FTIR and millimetre-wave measurements revealed significant amounts of ClO over Kiruna after the final warming in February 2001. In fact, column amounts of ClO were still increased in March 2001 when temperatures were about 20 K above the PSC (Polar Stratospheric Clouds) threshold. At these temperatures, chlorine activation due to heterogeneous processes on PSCs is not possible even in the presence of strong lee wave effects. In order to discuss possible reasons of this feature, time series of other chemical species will be presented and discussed, too. Measurements of HF and COF2 indicated that vortex air was still observed in mid-March 2001. Since the time series of HNO3 column amounts do not give any evidence of a denitrification later than 11 February, chlorine activation persisting for several weeks after the presence of PSCs due to denitrification is rather unlikely. The photolysis of ClONO2-rich air which had been formed at the end of February and beginning of March 2001 as well as chlorine activation due to the presence of an unusual aerosol layer are discussed as possible causes of the increased ClO column amounts after the final warming.
Lightning-produced NO2 observed by two ground-based UV-visible spectrometers at Vanscoy, Saskatchewan in August 2004
Authors: Fraser A. , Goutail F. , McLinden C. A. , Melo S. M. L. , Strong K.
Published: April 2010

Abstract. Ground-based measurements of ozone and NO2 slant columns by the SAOZ (Système d'Analyse par Observations Zénithales) and UT-GBS (University of Toronto Ground-Based Spectrometer) instruments during the MANTRA 2004 field campaign are presented herein. During the afternoon of 28 August, a thunderstorm passed over the instruments, which were installed at Vanscoy, Saskatchewan (52° N, 107° W). Enhanced slant columns of ozone and NO2 were observed by both instruments during the storm, with maximum values of two and 25 times the expected columns, respectively. The enhanced ozone slant columns are primarily due to the longer path traversed by the solar radiation caused by multiple scattering inside the thick cloud layer associated with the thunderstorm. The enhanced NO2 columns are attributed to NOx production by lightning. Two different methods are used to separate the NO2 enhancements into contributions from the longer path length and production by lightning. Combining the observed excess NO2 with lightning flash data from the Canadian Lightning Detection Network and Environment Canada Doppler radar measurements, the production of NO2 molecules per lightning flash is determined. Using these two methods, the best estimate of the production rate is found to be (7.45±1.38)×1026 molecules NO2/flash from the UT-GBS and (6.58±1.21)×1026 molecules NO2/flash from SAOZ. These results are consistent with previous estimates which range from 1026 molecules NO2/flash (Noxon, 1976) to (7±3)×1026 molecules NO2/flash (Franzblau and Popp, 1989).
On the variability of the Ring effect in the near ultraviolet: understanding the role of aerosols and multiple scattering
Authors: Langford A. O. , Schofield R. , Daniel J. S. , Portmann R. W. , Melamed M. L. , Miller H. L. , Dutton E. G. , Solomon S.
Published: April 2010

Abstract. The "filling-in'' (FI) of Fraunhofer lines, often referred to as the Ring effect, was examined using measurements of near ultraviolet sunlight scattered from the zenith sky above Boulder, Colorado during July and August 2005. The FI of the 344.1 nm Fe I line was directly determined by comparing direct sun and cloud-free zenith sky spectra recorded on the same day. The results, obtained over solar zenith angles (SZA) from 20 to 70°, are compared to the predictions of a simple Rotational Raman Scattering (RRS) spectral model. The measured FI was found to be up to 70% greater than that predicted by first-order molecular scattering with a much stronger SZA dependence. Simultaneously measured aerosol optical depths and Monte Carlo calculations show that the combination of aerosol scattering and second-order molecular scattering can account for these differences, and potentially explain the contradictory SZA dependences in previously published measurements of FI. These two scattering processes also introduce a wavelength dependence to FI that complicates the fitting of diffuse sunlight observations in differential optical absorption spectroscopy (DOAS). A simple correction to improve DOAS retrievals by removing this wavelength dependence is described.