bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comment on “Improving the seasonal cycle and interannual variations of biomass burning aerosol sources&quot; by Generoso et al.
Authors: Ji Y. , Stocker E. 
Published: April 2010

Abstract. Generoso et al. (2003) suggest a method for improving current inventories of aerosol emission from biomass burning based on the Along Track Scanning Radiometer (ATSR) nighttime hot spot product. In order to show the validity and representative of the nighttime burning product for such applications, Genoroso et al. (2003) compared the ATSR nighttime products to the daily fire products from TRMM, AVHRR etc. in nine selected regions. Their analyses demonstrate that in most cases, the nighttime products show a seasonal cycle that is consistent with the daily observations. However, they noticed significant discrepancies in biomass seasonality between ATSR nighttime product and TRMM daily product in Sahel region. In a commentary paper, Giglio and Kendall (2003) clarify that the origin of TRMM fire data used in Generoso et al. (2003) is from TRMM Science Data and Information System (Ji and Stocker, 2002). We thank Giglio and Kendall for such clarifications that provide an opportunity for us to clarify several issues on the applications of TSDIS fire data.
Validation of SCIAMACHY tropospheric NO2-columns with AMAXDOAS measurements
Authors: Heue K.-P. , Richter A. , Wagner T. , Bruns M. , Burrows J. P. , v. Friedeburg C. , Lee W. D. , Platt U. , Pundt I. , Wang P. 
Published: April 2010

Abstract. Vertical and slant tropospheric NO2-columns from the new satellite instrument SCIAMACHY on ENVISAT are validated by measurements of the Airborne Multi AXis DOAS (AMAXDOAS) instrument on board the DLR Falcon. The results presented here were obtained in February 2003 on a flight over the Alps, the Po-Valley and the Mediterranean. The tropospheric vertical column measured by AMAXDOAS varied between 12.8 and 27.2*1015 molec/cm2 over the Po-Valley where SCIAMACHY data resulted in 14.4 to 27.5*1015 molec/cm2. Over less polluted areas a similarly good agreement was found. The overall correlation between the two datasets results in a slope of the linear fit of 0.89. The slight differences observed might be attributed to the different spatial resolution and the temporal mismatch between the measurements over the Po-Valley.
Actinometric measurements of NO2 photolysis frequencies in the atmosphere simulation chamber SAPHIR
Authors: Bohn B. , Rohrer F. , Brauers T. , Wahner A. 
Published: April 2010

Abstract. The simulation chamber SAPHIR at Forschungszentrum Jülich has UV permeable teflon walls facilitating atmospheric photochemistry studies under the influence of natural sunlight. Because the internal radiation field is strongly affected by construction elements, we use external, radiometric measurements of spectral actinic flux and a model to calculate mean photolysis frequencies for the chamber volume (Bohn and Zilken, 2004). In this work we determine NO2 photolysis frequencies j(NO2) within SAPHIR using chemical actinometry by injecting NO2 and observing the chemical composition during illumination under various external conditions. In addition to a photo-stationary approach, a time-dependent method was developed to analyse the data. These measurements had two purposes. Firstly, to check the model predictions with respect to diurnal and seasonal variations in the presence of direct sunlight and secondly to obtain an absolute calibration factor for the combined radiometry-model approach. We obtain a linear correlation between calculated and actinometric j(NO2). A calibration factor of 1.34±0.10 is determined, independent of conditions in good approximation. This factor is in line with expectations and can be rationalised by internal reflections within the chamber. Taking into account the uncertainty of the actinometric j(NO2), an accuracy of 13% is estimated for the determination of j(NO2) in SAPHIR. In separate dark experiments a rate constant of (1.93±0.12)×10−14 cm3 s−1 was determined for the NO+O3 reaction at 298 K using analytical and numerical methods of data analysis.
The UV-A and visible solar irradiance spectrum: inter-comparison of absolutely calibrated, spectrally medium resolution solar irradiance spectra from balloon- and satellite-borne measurements
Authors: Gurlit W. , Bösch H. , Bovensmann H. , Burrows J. P. , Butz A. , Camy-Peyret C. , Dorf M. , Gerilowski K. , Lindner A. , Noël S. , Platt U. , Weidner F. , Pfeilsticker K. 
Published: April 2010

Abstract. Within the framework of the ENVISAT/-SCIAMACHY satellite validation, solar irradiance spectra are absolutely measured at moderate resolution in the UV/visible spectral range (in the UV from 316.7–418 nm and the visible from 400–652 nm at a full width half maximum resolution of 0.55 nm and 1.48 nm, respectively) from aboard the azimuth-controlled LPMA/DOAS balloon gondola at around 32 km balloon float altitude. After accounting for the atmospheric extinction due to Rayleigh scattering and gaseous absorption (O3, and NO2), the measured solar spectra are compared with previous observations. Our solar irradiance is +1.6% larger than the re-calibrated Kurucz et al. (1984) solar spectrum (Fontenla et al., 1999, called MODTRAN 3.5) in the visible spectral range (435–650 nm), +1.5% larger in the (370–415 nm) wavelength interval, but −4% smaller in the UV spectral range (316.7–370 nm), when the Kurucz spectrum is convolved to the spectral resolution of our instrument. The same comparison with the SOLSPEC solar spectrum (Thuillier et al., 1997, 1998a, b) confirms the somewhat larger solar irradiance (+1.7%) measured by the balloon instrument from 435–500 nm, but not from 500–650 nm, where the SOLSPEC is −1.3% lower than MODTRAN 3.5. Comparison of the SCIAMACHY solar spectrum from channels 1 to 4 (– re-calibrated by the University of Bremen –) with MODTRAN 3.5 indicates an agreement of +0.2% in the visible spectral range (435–585 nm). With this calibration, the SCIAMACHY solar spectrum is congruent with the balloon observations (−1%) in the 316.7–370 nm wavelength range, but both are up to −5%/−3% smaller than MODTRAN 3.5 and SOLSPEC, respectively. In agreement with findings of Skupin et al. (2002) our study emphasizes that the present ESA SCIAMACHY level 1 calibration is systematically +15% larger in the considered wavelength intervals when compared to all available other solar irradiance measurements.
Atmospheric number size distributions of soot particles and estimation of emission factors
Authors: Rose D. , Wehner B. , Ketzel M. , Engler C. , Voigtländer J. , Tuch T. , Wiedensohler A. 
Published: April 2010

Abstract. Number fractions of externally mixed particles of four different sizes (30, 50, 80, and 150 nm in diameter) were measured using a Volatility Tandem DMA. The system was operated in a street canyon (Eisenbahnstrasse, EI) and at an urban background site (Institute for Tropospheric Research, IfT), both in the city of Leipzig, Germany as well as at a rural site (Melpitz (ME), a village near Leipzig). Intensive campaigns of 3–5 weeks each took place in summer 2003 as well as in winter 2003/2004. The data set thus obtained provides mean number fractions of externally mixed soot particles of atmospheric aerosols in differently polluted areas and different seasons (e.g. at 80 nm on working days, 60% (EI), 22% (IfT), and 6% (ME) in summer and 26% (IfT), and 13% (ME) in winter). Furthermore, a new method is used to calculate the size distribution of these externally mixed soot particles from parallel number size distribution measurements. A decrease of the externally mixed soot fraction with decreasing urbanity and a diurnal variation linked to the daily traffic changes demonstrate, that the traffic emissions have a significant impact on the soot fraction in urban areas. This influence becomes less in rural areas, due to atmospheric mixing and transformation processes. For estimating the source strength of soot particles emitted by vehicles (veh), soot particle emission factors were calculated using the Operational Street Pollution Model (OSPM). The emission factor for an average vehicle was found to be (1.5±0.4)·1014 #/(km·veh). The separation of the emission factor into passenger cars ((5.8±2)·1013 #/(km·veh)) and trucks ((2.5±0.9)·1015 #/(km·veh)) yielded in a 40-times higher emission factor for trucks compared to passenger cars.
A review of biomass burning emissions, part I: gaseous emissions of carbon monoxide, methane, volatile organic compounds, and nitrogen containing compounds
Authors: Koppmann R. , von Czapiewski K. , Reid J. S. 
Published: April 2010

Abstract. Biomass burning is the burning of living and dead vegetation. Ninety percent of all biomass-burning events are thought to be human initiated. Human induced fires are used for a variety of ''applications'' such as agricultural expansion, deforestation, bush control, weed and residue burning, and harvesting practices. Natural fires are grassland and forest fires mainly induced by lightning. It is estimated that 8700 Tg of dry matter/year are burnt each year in total. Emissions from biomass burning include a wide range of gaseous compounds and particles that contribute significantly to the tropospheric budgets on a local, regional, and even global scales. The emission of CO, CH4 and VOC affect the oxidation capacity of the troposphere by reacting with OH radicals, and emissions of nitric oxide and VOC lead to the formation of ozone and other photo oxidants. For a large number of compounds biomass burning is one of the largest single sources in the troposphere, especially in the tropics. Biomass-burning emissions play an important role in the biogeochemical cycles of carbon and nitrogen. Following the first systematic investigations on fire emissions in laboratory experiments in the 1960's, the last 20 years saw an increasing number in studies on biomass-burning emissions in various ecosystems. Recently, our knowledge of the emissions of gaseous compounds in the troposphere from fires has increased considerably. This manuscript is the first of four describing the properties biomass burning emissions. The properties of biomass-burning particles are discussed in part II and III of this review series which have been recently published, and their direct radiative effects are in part IV. This paper focuses on the review of emission ratios and emission rates of carbon monoxide, methane, volatile organics, and nitrogen containing compounds and should not be seen as a review of global emission estimates, even though we discuss the implications of our results on such studies.
Conceptual study on nucleation burst evolution in the convective boundary layer – Part IV: Comparison with previous observations
Authors: Hellmuth O. 
Published: April 2010

Abstract. In part I to III of the present paper a revised columnar high-order modelling approach to model gas-aerosol interactions in the convective boundary layer (CBL) was proposed, and simulation results of two nucleation scenarios (binary vs. ternary) on new particle formation (NPF) in the anthropogenically influenced CBL were presented. It was demonstrated that both scenarios strongly differ with respect to the amplitude and phase of the NPF burst detectable in the Prandtl layer, as well as with respect to the time-height evolution of turbulent vertical fluxes and double correlation terms of physico-chemical and aerosoldynamical variables. In the present part, an attempt is made to re-evaluate previous observations of NPF bursts in the CBL in view of the scenario simulations discussed in part III. Special attention is payed to the role of CBL turbulence in NPF burst evolution. At first, a compilation of empirical findings and hypothesis on NPF in the CBL derived from a number of field experiments, is performed. Secondly, it is demonstrated, that the binary scenario simulated in part III corresponds well to a number of NPF burst events observed in Hyytiälä (Finland) and Melpitz (Eastern Germany). Here, one of the key hypothesis on the role of turbulence in NPF is confirmed. Other NPF events, such as those observed at Hohenpeissenberg, a mountain site (Southern Germany), can not yet be conclusively explained. To note, that the results of previous box modelling studies to explain NPF events at Hohenpeissenberg are not unambiguous. Nonetheless, based on only two simulated scenarios it is demonstrated, that a columnar high-order model is a helpful tool to elucidate the genesis of NPF bursts frequently observed in the CBL. A comprehensive verification/validation study using observed high-order moments as well as further scenario simulations remain to be performed.
Measurements of optical properties of atmospheric aerosols in Northern Finland
Authors: Aaltonen V. , Lihavainen H. , Kerminen V.-M. , Komppula M. , Hatakka J. , Eneroth K. , Kulmala M. , Viisanen Y. 
Published: April 2010

Abstract. Three years of continuous measurements of aerosol optical properties and simultaneous aerosol number size distribution measurements at Pallas GAW station, a remote subarctic site in the northern border of the boreal forest zone, have been analysed. The scattering coefficient at 550 nm varied from 0.2 to 94.4 Mm−1 with an average of 7.1±8.6 Mm−1. Both the scattering and backscattering coefficients had a clear seasonal cycle with an autumn minimum and a 4–5 times higher summer maximum. The scattering was dominated by submicron aerosols and especially so during late summer and autumn. The Ångström exponent had a clear seasonal pattern with maximum values in late summer and minimum values during wintertime. The highest hemispheric backscattering fraction values were observed in autumn, indicating clean air with few scattering particles and a particle size distribution strongly dominated by ultrafine particles. To analyse the influence of air mass origin on the aerosol optical properties a trajectory climatology was applied to the Pallas aerosol data. The most polluted trajectory patterns represented air masses from the Kola Peninsula, Scandinavia and Russia as well as long-range transport from Britain and Eastern Europe. These air masses had the largest average scattering and backscattering coefficients for all seasons. Higher than average values of the Ångström exponent were also observed in connection with transport from these areas.
Atmospheric transport and deposition of Indonesian volcanic emissions
Authors: Pfeffer M. A. , Langmann B. , Graf H.-F. 
Published: April 2010

Abstract. A regional climate model study has been performed to investigate the transport and atmospheric loss rates of emissions from Indonesian volcanoes and the sensitivity of these emissions to meteorological conditions and the solubility of the released emissions. Two experiments were conducted: 1) volcanic sulfur released as primarily SO2 and oxidation to SO42− determined by considering the major tropospheric chemical reactions; and 2) PbCl2 released as an infinitely soluble passive tracer. The first experiment was used to calculate SO2 loss rates from each active volcano resulting in an annual mean loss rate for all volcanoes of 1.1×10−5 s−1, or an e-folding rate of approximately 1 day. SO2 loss rate was found to vary seasonally, be poorly correlated with wind speed, and uncorrelated with temperature or relative humidity. The variability of SO2 loss rates is found to be correlated with the variability of wind speeds, suggesting that it is much more difficult to establish a ''typical'' SO2 loss rate for volcanoes that are exposed to inconsistent winds. Within an average distance of 69 km away from the active Indonesian volcanoes, 53% of SO2 is lost due to conversion to SO42−, 42% due to dry deposition, and 5% is lost due to lateral transport away from the dominant direction of plume travel. The solubility of volcanic emissions in water is shown to have a major influence on their atmospheric transport and deposition. High concentrations of PbCl2 are predicted to be deposited near to the volcanoes while volcanic S travels further away until removal from the atmosphere primarily via the wet deposition of H2SO4. The ratio of the concentration of PbCl2 to SO2 is found to exponentially decay at increasing distance from the volcanoes. The more rapid removal of highly soluble species should be considered when making observations of SO2 in an aged plume and relating this concentration to other volcanic species. An assumption that the ratio between the concentrations of highly soluble volcanic compounds and S within an aged plume is equal to that observed in fumarolic gases will result in an overestimation of the atmospheric concentration of highly soluble species.
Concentrations of OH and HO2 radicals during NAMBLEX: measurements and steady state analysis
Authors: Smith S. C. , Lee J. D. , Bloss W. J. , Johnson G. P. , Heard D. E. 
Published: April 2010

Abstract. OH and HO2 concentrations were measured simultaneously at the Mace Head Atmospheric Research Station in the summer of 2002 during the NAMBLEX (North Atlantic Marine Boundary Layer EXperiment) field campaign. OH was measured by laser-induced fluorescence employing the FAGE (Fluorescence Assay by Gas Expansion) technique, with a mean daytime detection limit of 2.7×105 molecule cm−3 (5 min acquisition period; signal-to-noise ratio = 1). HO2 was detected as OH following its chemical conversion through addition of NO, with a mean detection limit of 4.4×106 molecule cm−3. The diurnal variation of OH was measured on 24 days, and that of HO2 on 17 days. The local solar noon OH concentrations ranged between (3–8)×106 molecule cm−3, with a 24 h mean concentration of 9.1×105 molecule cm−3. The local solar noon HO2 concentrations were (0.9–2.1)×108 molecule cm−3 (3.5–8.2 pptv), with a 24 h mean concentration of 4.2×107 molecule cm−3. HO2 radicals in the range (2–3)×107 molecule cm−3 were observed at night. During NAMBLEX, a comprehensive suite of supporting measurements enabled a detailed study of the behaviour of HOx radicals under primarily clean marine conditions. Case study periods highlight the typical radical levels observed under different conditions. Steady state expressions are used to calculate OH and HO2 concentrations and to evaluate the effect of different free-radical sources and sinks. The diurnally averaged calculated to measured OH ratio was 1.04±0.36, but the ratio displays a distinct diurnal variation, being less than 1 during the early morning and late afternoon/evening, and greater than 1 in the middle of the day. For HO2 there was an overprediction, with the agreement between calculated and measured concentrations improved by including reaction with measured IO and BrO radicals and uptake to aerosols. Increasing the concentration of IO radicals included in the calculations to above that measured by a DOAS instrument with an absorption path located mainly over the ocean, reflecting the domination of the inter-tidal region as an iodine source at Mace Head, led to further improvement. The results are compared with previous measurements at Mace Head, and elsewhere in the remote marine boundary layer.
Estimating the contribution of bromoform to stratospheric bromine and its relation to dehydration in the tropical tropopause layer
Authors: Sinnhuber B.-M. , Folkins I. 
Published: April 2010

Abstract. The contribution of bromoform to the stratospheric bromine loading is estimated using the one-dimensional tropical mean model of Folkins and Martin (2005), which is constrained by observed mean profiles of temperature and humidity. In order to reach the stratosphere, bromoform needs to be lifted by deep convection into the tropical tropopause layer (TTL), above the level of zero radiative heating. The contribution of bromoform to stratospheric bromine depends then critically on the rate of removal of the degradation products of bromoform (collectively called Bry here) from the TTL, which is believed to be due to scavenging by falling ice. This relates the transport of short-lived bromine species into the stratosphere to processes of dehydration in the TTL. In the extreme case of dehydration occurring only through overshooting deep convection, the loss of Bry from the TTL may be negligible and consequently bromoform will fully contribute with its boundary layer mixing ratio to the stratospheric bromine loading, i.e. with 3 pptv for an assumed 1 pptv of bromoform in the boundary layer. For the other extreme that Bry is removed from the TTL almost instantaneously, the model calculations predict a contribution of about 0.5 pptv for the assumed 1 pptv of boundary layer bromoform. While this gives some constraints on the contribution of bromoform to stratospheric bromine, it is argued that a more precise number cannot be given until the mechanisms of dehydration in the TTL are better understood.
Technical note: The libRadtran software package for radiative transfer calculations – description and examples of use
Authors: Mayer B. , Kylling A. 
Published: April 2010

Abstract. The libRadtran software package is a suite of tools for radiative transfer calculations in the Earth's atmosphere. Its main tool is the uvspec program. It may be used to compute radiances, irradiances and actinic fluxes in the solar and terrestrial part of the spectrum. The design of uvspec allows simple problems to be easily solved using defaults and included data, hence making it suitable for educational purposes. At the same time the flexibility in how and what input may be specified makes it a powerful and versatile tool for research tasks. The uvspec tool and additional tools included with libRadtran are described and realistic examples of their use are given. The libRadtran software package is available from same http://www.libradtran.org.
Measurements of Saharan dust aerosols over the Eastern Mediterranean using elastic backscatter-Raman lidar, spectrophotometric and satellite observations in the frame of the EARLINET project
Authors: Papayannis A. , Balis D. , Amiridis V. , Chourdakis G. , Tsaknakis G. , Zerefos C. , Castanho A. D. A. , Nickovic S. , Kazadzis S. , Grabowski J. 
Published: April 2010

Abstract. We report on the vertical distributions of Saharan dust aerosols over the N.E. Mediterranean region, which were obtained during a typical dust outbreak on August 2000, by two lidar systems located in Athens and Thessaloniki, Greece, in the frame of the European EARLINET project. MODIS and ground sun spectrophotometric data, as well as air-mass backward trajectories confirmed the existence of Saharan dust in the case examined, which was also successfully forecasted by the DREAM dust model. The lidar data analysis for the period 2000–2002 made possible, for the first time, an estimation of the vertical extent of free tropospheric dust layers (mean values of the aerosol backscatter and extinction coefficients and the extinction-to-backscatter ratio (lidar ratio, LR) at 355 nm), as well as a seasonal distribution of Saharan dust outbreaks over Greece, under cloud-free conditions. A mean value of the lidar ratio at 355 nm was obtained over Athens (52.81±1.02 sr) and over Thessaloniki (44.19±1.72 sr) during the Saharan dust outbreaks. The corresponding aerosol optical thickness (AOT) at 355 nm, in the altitude range 0–5 km, was 0.69±0.12 and 0.65±0.10 for Athens and Thessaloniki, respectively (within the dust layer the AOT was 0.23 and 0.21, respectively). Air-mass back-trajectory analysis performed in the period 2000–2002 for all Saharan dust outbreaks over the N. E. Mediterranean indicated the main pathways followed by the dust aerosols.