Brigitte Buchmann - Academia.edu (original) (raw)

Papers by Brigitte Buchmann

Im Unterschied zu Forschungsinfrastrukturen in anderen Disziplinen, zeichnen sich Forsch... more Im Unterschied zu Forschungsinfrastrukturen in anderen Disziplinen, zeichnen sich Forschungsinfrastrukturen für Umweltbeobachtungen in der Regel durch langfristige Messungen zahlreicher Parameter mit verschiedenen Instrumenten an unterschiedlichen Orten aus. Bodengestützte, atmosphärische Beobachtungen von Luftschadstoffen und Klimagasen können unterschiedliche Ziele verfolgen, wie zum Beispiel die Überwachung regulatorischer Massnahmen und die Einhaltung von Grenzwerten, die wissenschaftliche Untersuchung von Variabilitäten und Trends, die Validierung von Modellrechnungen und Satellitenbeobachtungen oder die Früherkennung von neu auftretenden Substanzen. Die Qualitätskontrolle und Qualitätssicherung müssen nicht nur dem dezentralen Charakter der Beobachtungen Rechnung tragen, sondern auch sicherstellen, dass die der Fragestellung angepassten Datenqualitätsziele erreicht werden. Zusätzlich müssen Beobachtungen, die Teil von mehreren Messnetzen und Infrastrukturen sind, verschiedene Kriterien erfüllen, z.B. im Hinblick auf das Normal der Rückführbarkeit, die Präzision, aber auch bezüglich Dokumentation und Bereitstellung der Resultate in Datenbanken. Die Präsentation gibt einen Überblick über die langfristigen Luftqualitätsmessungen in der Schweiz im Rahmen des Nationalen Beobachtungsnetzes für Luftfremdstoffe (NABEL), ihre Einbettung in das European Monitoring and Evaluation Programme (EMEP), die Kooperation mit den europäischen Forschungsinfrastrukturen ICOS (Integrated Carbon Observation System) und ACTRIS (Aerosols, Clouds, and Trace gases Research Infrastructure Network), und die Zusammenarbeit in globalen Aktivitäten wie dem Advanced Global Atmospheric Gases Experiment (AGAGE) zur kontinuierlichen Messung von klimawirksamen und ozonabbauenden Substanzen und dem von der Weltorganisation für Meteorologie (WMO) koordinierten Global Atmosphere Watch (GAW) Programm.

Globally consistent in situ-observations of high precision and known quality are one key element ... more Globally consistent in situ-observations of high precision and known quality are one key element in understanding global climate change and effects of human activity on the Earth's atmosphere. The spatial coverage of available data strongly depends on the species of interest and varies highly around the globe. In case of surface ozone (O 3), the observational network is particularly sparse in Africa, Asia, and South America. The southern hemispheric pristine GAW-regional station "El Tololo", located in the foothills of the Chilean Andes (30.17 • S, 70.80 • W, 2220 m asl), has been equipped with an ozone photometer in 1995 and has since then been measuring tropospheric ozone permanently. However, these measurements were neither entirely systematically processed nor quality-controlled until recently. This situation was drastically improved in 2015 the framework of the Capacity Building and Twinning for Climate Observing Systems (CATCOS) project (www.meteoswiss.ch/catcos). Empa, in coordination with the local operator, Dirección Meteorológica de Chile (DMC), and the University of Santiago, revised the entire surface ozone measurements. The unique 20-year-long ozone data-set has been made publicly available on the World Data Centre for Greenhouse Gases (WDCGG, Japan) in mid-2015 and represents an exceptional piece of information on the southern hemispheric surface ozone distribution. In contrary to northern hemispheric stations, the positive trend in the measurements of tropospheric ozone at "El Tololo" did not level off in the recent past. More specifically, "El Tololo" shows a steady positive trend of 0.7 ppb/decade in agreement with other stations on the Southern hemisphere. However, the seasonal cycle differs strongly in behaviour, as maximum values in ozone do not peak in austral winter, but in austral spring-most probably due to stratospheric influence. We also find that the spring maximum has a retrograding tendency of around 5 days per decade. A combined analysis of SHADOZ ozone soundings and GAW surface ozone measurements of the southern hemisphere shows two general trends, which are confirmed by the El-Tololo-dataset: With increasing altitude, the maximum values of the seasonal cycle occur earlier in the year. On the other hand, the amplitude between lowest and highest values decreases with increasing latitude. The presentation will provide a comprehensive overview of the extensive analysis of the perennial O 3 record at "El Tololo" in comparison with other southern hemispheric monitoring stations. The contributions from stratosphere-troposphere-exchange, from variations in the tropospheric background, and from photochemical production will be discussed to identify and quantify the key processes driving the variations of surface ozone concentrations at this remote and elevated location in the southern hemisphere.

Journal of Aerosol Science, 2004

CHIMIA International Journal for Chemistry, 2016

Environmental Science & Technology, 2009

Hourly trace element measurements were performed in an urban street canyon and next to an interur... more Hourly trace element measurements were performed in an urban street canyon and next to an interurban freeway in Switzerland during more than one month each, deploying a rotating drum impactor (RDI) and subsequent sample analysis by synchrotron radiation X-ray fluorescence spectrometry (SR-XRF). Antimony and other brake wear associated elements were detected in three particle size ranges (2.5-10, 1-2.5, and 0.1-1 µm). The hourly measurements revealed that the effect of resuspended road dust has to be taken into account for the calculation of vehicle emission factors. Individual values for light and heavy duty vehicles were obtained for stopand-go traffic in the urban street canyon. Mass based brake wear emissions were predominantly found in the coarse particle fraction. For antimony, determined emission factors were 11 (7 and 86 (42 µg km-1 vehicle-1 for light and heavy duty vehicles, respectively. Antimony emissions along the interurban freeway with free-flowing traffic were significantly lower. Relative patterns for brake wear related elements were very similar for both considered locations. Beside vehicle type specific brake wear emissions, road dust resuspension was found to be a dominant contributor of antimony in the street canyon.

Environmental Science & Technology, 2008

Atmospheric Measurement Techniques, 2010

Surface reflectance is a key parameter in satellite trace gas retrievals in the UV/visible range ... more Surface reflectance is a key parameter in satellite trace gas retrievals in the UV/visible range and in particular for the retrieval of nitrogen dioxide (NO 2) vertical tropospheric columns (VTCs). Current operational retrievals rely on coarse-resolution reflectance data and do not account for the generally anisotropic properties of surface reflectance. Here we present a NO 2 VTC retrieval that uses MODIS bidirectional reflectance distribution function (BRDF) data at high temporal (8 days) and spatial (1 km × 1 km) resolution in combination with the LIDORT radiative transfer model to account for the dependence of surface reflectance on viewing and illumination geometry. The method was applied to two years of NO 2 observations from the Ozone Monitoring Instrument (OMI) over Europe. Due to its wide swath, OMI is particularly sensitive to BRDF effects. Using representative BRDF parameters for various land surfaces, we found that in July (low solar zenith angles) and November (high solar zenith angles) and for typical viewing geometries of OMI, differences between MODIS black-sky albedos and surface bi-directional reflectances are of the order of 0-10% and 0-40%, respectively, depending on the position of the OMI pixel within the swath. In the retrieval, black-sky albedo was treated as a Lambertian (isotropic) reflectance, while for BRDF effects we used the kernel-based approach in the MODIS BRDF product. Air Mass Factors were computed using the LIDORT radiative transfer model based on these surface reflectance conditions. Differences in NO 2 VTCs based on the Lambertian and BRDF approaches were found to be of the order of 0-3% in July and 0-20% in November with the extreme values found at large viewing angles. The much larger differences in November are

Atmospheric Environment, 2003

The urban airshed of Turkey is under the influence of both traffic and heating emissions. Periodi... more The urban airshed of Turkey is under the influence of both traffic and heating emissions. Periodic monitoring and management of air pollution is a must for an up-to-date exposure assessment for effective health and environmental management. The main objective of this paper is to assess the spatial and temporal variability of particulate matter (PM 10) in urban areas of Turkey using the metropolitan area of Ankara as a case study, exploring the seasonal variation of PM 10 concentrations resulting from indoor heating and transport. This study employed spatiotemporal kriging with external drift to examine the space-time variability and distribution of PM 10 concentrations in Ankara for year 2015. The measurements of PM 10 in and around metropolitan Ankara were carried out at nine stations. Measurements for the

Atmospheric Chemistry and Physics, 2010

Long-term, ground based in-situ observations of ozone (O 3) and its precursor gases nitrogen diox... more Long-term, ground based in-situ observations of ozone (O 3) and its precursor gases nitrogen dioxide (NO 2) and carbon monoxide (CO) from the four sites Hohenpeissenberg and Zugspitze (D), Sonnblick (A) and Jungfraujoch (CH) are presented for the period 1995-2007. These Central European alpine mountain observatories cover an altitude range of roughly 1000 to 3500 m. Comparable analytical methods and common quality assurance (QA) procedures are used at all sites. For O 3 and CO, calibration is linked to primary calibrations (O 3) or CO standards provided by the Central Calibration Laboratory (CCL) at NOAA/ESRL. All stations have been audited by the World Calibration Centre (WCC) for CO and O 3 (WCC-Empa; CH). Data from long-term measurements of NO 2 and CO are only available from Hohenpeissenberg and Jungfraujoch. Both sites show slightly decreasing mixing ratios of the primarily emitted NO 2 and the partly anthropogenically emitted CO between 1995 and 2007. The findings are generally consistent with shorter observation periods at Zugspitze and Sonnblick and thus are considered to represent regional changes in Central European atmospheric composition at this altitude range. Over the same period, 1995-2007, the O 3 mixing ratios have slightly increased at three of the four sites independent of wind sector. Trends are often more pronounced in winter and less in summer; highest declines of NO 2 and CO are observed in winter and the lowest in summer, whereas the strongest O 3 increase was detected in winter and lowest or even decline in summer, respectively. Weekly cycles demonstrate anthropogenic impact at all elevations with enhanced NO 2 on working days compared to weekends. Enhanced O 3

Atmospheric Chemistry and Physics, 2005

High tropospheric NO 2 amounts are occasionally detected by space-borne spectrometers above cloud... more High tropospheric NO 2 amounts are occasionally detected by space-borne spectrometers above cloudy scenes. For monitoring of near-ground air pollution such data are not directly applicable because clouds shield the highly polluted planetary boundary layer (PBL). We present a method based on trajectories which implicitly estimates the additional subcloud NO 2 distribution in order to model concentrations at ground stations. The method is applied to a transboundary pollution transport episode which led to high NO 2 vertical tropospheric column densities (VTCs) over middle Europe observed by the Global Ozone Monitoring Experiment (GOME) instrument above clouds on 17 February 2001. The case study shows that pollution originally residing near the ground in central Germany, the Ruhr area and adjacent parts of the Netherlands and Belgium has been advected to higher tropospheric levels by a passing weather front. Combining the above-cloud NO 2 VTCs with trajectory information covering the GOME columns and including their sub-cloud part yields an estimate of the total NO 2 distribution within the tropospheric columns. The highly polluted air masses are then traced by forward trajectories starting from the GOME columns to move further to the Alpine region and their impact there is assessed. Considering ground-based in-situ measurements in the Alpine region, we conclude that for this episode, at least 50% of the NO 2 concentration recorded at the sites can be attributed to transboundary transport during the frontal passage. This study demonstrates the potential of using NO 2 VTCs from GOME detected above clouds when combined with transport modelling.

ABSTRACT The GHG-CCI project is one of several projects of ESA's Climate Change Initiativ... more ABSTRACT The GHG-CCI project is one of several projects of ESA's Climate Change Initiative (CCI), which will deliver various Essential Climate Variables (ECVs). The goal of GHG-CCI is to deliver global satellite-derived data sets of the two most important anthropogenic greenhouse gases (GHGs) carbon dioxide (CO2) and methane (CH4) suitable to obtain information on regional CO2 and CH4 surface sources and sinks as needed for better climate prediction. The GHG-CCI core ECV data products are column-averaged mole fractions of CO2 and CH4, i.e., XCO2 and XCH4, retrieved from SCIAMACHY on ENVISAT and TANSO on GOSAT. Other satellite instruments will be used to provide constraints in upper layers such as IASI, MIPAS, and ACE-FTS. Which of the advanced algorithms, which are under development, will be the best for a given data product still needs to be determined. For each of the 4 GHG-CCI core data products - XCO2 and XCH4 from SCIAMACHY and GOSAT - several algorithms will be further developed and the corresponding data products will be inter-compared to identify which data product is the most appropriate. This includes comparisons with corresponding data products generated elsewhere, most notably with the operational data products of GOSAT generated at NIES and the NASA/ACOS GOSAT XCO2 product. This activity, the so-called "Round Robin exercise", will be performed in the first two years of this project. At the end of the 2 year Round Robin phase a decision will be made which of the algorithms performs best. The selected algorithms will be used to generate the first version of the ECV GHG. In the last six months of this 3 year project the resulting data products will be validated and made available to all interested users. In the presentation and overview about this project will be given. Focus will be on a discussion and intercomparison of the various data products focusing on CO2.

Helvetica Chimica Acta, 1987

On protonation of the diolefin complexes [M(C5R5)(diene)] (R = H, CH3; M = Co, Rh, Ir; diene = 2,... more On protonation of the diolefin complexes [M(C5R5)(diene)] (R = H, CH3; M = Co, Rh, Ir; diene = 2,3‐dimethylbutadiene, 1,3‐cyclohexadiene) with HBF4, cationic species are isolated which, at room temperature, show fluxional behaviour on the NMR time scale. Depending on R and M, three different ground states are observed for these cationic complexes in the NMR spectra at low temperatures. While for M = Ir a classical metal‐hydride structure M–H is observed, the Co and Rh complexes show ground states with ‘agostic’ H‐bridges M‥H‥C. The protonated species are characterized by 1H‐, 13C‐ and 103Rh‐NMR spectra. Total line‐shape analysis of the 1H and 13C spectra in the 298–154 K range gave the free enthalpies of activation ΔG ≠ for methyl rotation and 1, 4‐H shift in the agostic structures 2b, 2b′, 2c, and 2c′. The Rh complexes show the lowest ΔG± values for the 1,4‐H shift, and the strength of the agostic bond appears to decrease in the order CoC5H5 > CoC5Me5 > RhC5H5 > RhC5Me5. O...

Atmospheric Chemistry and Physics, 2009

Despite the importance of carbon monoxide (CO) for the overall oxidative capacity of the atmosphe... more Despite the importance of carbon monoxide (CO) for the overall oxidative capacity of the atmosphere, there is still considerable uncertainty in ambient measurements of CO. To address this issue, an inter-comparison between four different measurement techniques was made over a period of two months at the high-alpine site Jungfraujoch (JFJ), Switzerland. The measurement techniques were Nondispersive Infrared Absorption (NDIR), Vacuum UV Resonance Fluorescence (VURF), gas chromatographic separation with a mercuric oxide reduction detector (GC/HgO), and gas chromatographic separation followed by reduction on a nickel catalyst and analysis by a flame ionization detector (GC/FID). The agreement among all techniques was better than 2% for one-hourly averages, which confirmed the suitability of the NDIR method for CO measurements even at remote sites. The inter-comparison added to the validation of the 12-year record (1996-2007) of continuous CO measurements at JFJ. To date this is one of the longest time series of continuous CO measurements in the free troposphere over Central Europe. This data record was further investigated with a focus on trend analysis. A significant negative trend was observed at JFJ showing a decrease of 21.4±0.3% over the investigated period, or an average annual decrease of 1.78%/yr (2.65±0.04 ppb/yr). These results were compared with emission inventory data reported to the Longrange Transboundary Air Pollution (LRTAP) Convention. It could be shown that long range transport significantly influences the CO levels observed at JFJ, with air masses of non-European origin contributing at least one third of the observed mole fractions.

The distribution of short-lived air pollutants such as NO2 is closely tied to geographically fixe... more The distribution of short-lived air pollutants such as NO2 is closely tied to geographically fixed emission sources. Variations due to changing weather conditions or emission strengths may be considered as noisy deviations from a mean picture. In this study we investigate to what extent fine scale details of (NO2) air pollution structures can be reconstructed from coarsely resolved satellite observations. For this we set up an idealized test environment where both the original distribution to be reconstructed and the level of noise of the observations are known, and apply a number of iterative image reconstruction algorithms originally developed for application in computer tomography. In the case of noise-free observations, the original distribution can be completely recovered except for spatial frequencies where the spectrum of the aperture function (the pixel rectangle) exhibits nulls. For noisy observations the situation is more complicated and the success of reconstruction criti...

Monitoring of atmospheric trace gases is of importance to observe trends and to confirm the succe... more Monitoring of atmospheric trace gases is of importance to observe trends and to confirm the success of measures taken to reduce air pollution. The extension of ground-based monitoring networks with satellite observations will be an important step to exploit the new technologies in order to reach this aim. After an introduction of the Swiss National Air Pollution Monitoring Network (NABEL),

Ziel dieser Untersuchung, welche von der Eidgenoessischen Materialpruefungs- und Forschungsanstal... more Ziel dieser Untersuchung, welche von der Eidgenoessischen Materialpruefungs- und Forschungsanstalt (EMPA) gemeinsam mit dem Paul Scherrer Institut (PSI) durchgefuehrt wurde, war die Quantifizierung und Charakterisierung der primaeren Partikel-Emissionen aus dem Strassenverkehr sowie die Berechnung von Emissionsfaktoren fuer verschiedene Verkehrssituationen und Prozesse (Auspuffemissionen, Emissionen aus Abrieb und Aufwirbelung). Hierzu wurden beiderseits von stark befahrenen Strassen Immissionsmessungen durchgefuehrt. Fuer meteorologische Situationen mit Querwind zur Strasse koennen aus Lee-Luv-Differenzen die Zusatzbelastungen bestimmt werden, die durch den lokal vorbeifahrenden Strassenverkehr verursacht werden. Wo wegen der zahlreichen einschraenkenden Randbedingungen das Lee-Luv-Konzept nicht zu realisieren war, wurden statt dessen die Differenzen eines direkt verkehrsbelasteten Standorts und eines nahe gelegenen "Hintergrundstandorts" gebildet und analog ausgewertet. ...

The EC project NORS (Demonstration Network Of ground-based Remote Sensing Observations in support... more The EC project NORS (Demonstration Network Of ground-based Remote Sensing Observations in support of the GMES Atmospheric Service) aims at demonstrating the value of ground-based remote sensing data for quality assessment and improvement of the GMES products. As part of NORS CO, CH4, O3 and NO2 tropospheric products as obtained by ground-based remote sensing within the Network for the Detection of Atmospheric Composition Change (NDACC) are compared to continuous surface in-situ measurements that are reported on common international reference scales within the Global Atmospheric Watch (GAW) Programme. However, a direct comparison between the different methods is hindered by different sampling volumes, introducing uncertainties due to representativeness.