Ozone stress as a driving force of sesquiterpene emissions: a suggested parameterisation

Sesquiterpenes (C15H24) are semi-volatile organic compounds emitted by vegetation and are of interest in atmospheric research because they influence the oxidative capacity of the atmosphere and contribute to the formation of secondary organic aerosols. However, little is known about their emission pattern and no established parameterisation is available for global emission models. The aim of this study is to investigate a Central European spruce forest and its emission response to meteorological and environmental parameters, looking for a parameterisation that incorporates heat and oxidative stress as the main driving forces of the induced emissions. Therefore, a healthy ca. 80 yr old Norway spruce (Picea abies) tree was selected and a dynamical vegetation enclosure technique was applied from April to November 2011. The emissions clearly responded to temperature changes with small variations in the β-factor along the year (βspring = 0.09 ± 0.01, βsummer = 0.12 ± 0.02, βautumn = 0.11 ± 0.02). However, daily calculated values revealed a vast amount of variability in temperature dependencies ((0.02 ± 0.002) < β < (0.27 ± 0.04)) with no distinct seasonality. By separating the complete dataset in 10 different ozone regimes, we found that in moderately or less polluted atmospheric conditions the main driving force of sesquiterpene emissions is the temperature, but when ambient ozone mixing ratios exceed a critical threshold of (36.6 ± 3.9) ppbv, the emissions become primarily correlated with ozone. Considering the complete dataset, cross correlation analysis resulted in highest correlation with ambient ozone mixing ratios (CCO3 = 0.63 ± 0.01; CCT = 0.47 ± 0.02 at t = 0 h for temperature) with a time shift 2–4 h prior to the emissions. An only temperature dependent algorithm was found to substantially underestimate the induced emissions (20% of the measured; R2 = 0.31). However, the addition of an ozone dependent term improved substantially the fitting between measured and modelled emissions (81% of the modelled emissions could be explained by the measurements; R2 = 0.63), providing confidence about the reliability of the suggested parameterisation for the spruce forest site investigated

Ozone stress as a driving force of sesquiterpene emissions: a suggested parameterization [Discussion paper]

Sesquiterpenes (C15H24) are semi-volatile organic compounds emitted by vegetation and are of interest in atmospheric research because they influence the oxidative capacity of the atmosphere and contribute to the formation of secondary organic aerosols. However, little is known about their emission pattern and no established parameterization is available for global emission models. The aim of this study is to investigate a Central European spruce forest and its emission response to meteorological and environmental parameters, looking for a parameterization that incorporates heat and oxidative stress as the main driving forces of the induced emissions. Therefore, a healthy ca. 80 yr old Norway spruce (Picea abies) tree was selected and a dynamical vegetation enclosure technique was applied from April to November 2011. The emissions clearly responded to temperature changes with small variations in the β-factor along the year (βspring=0.09 ± 0.01, βsummer=0.12 ± 0.02, βautumn=0.11 ± 0.02). However, daily calculated values revealed a vast amount of variability in temperature dependencies ((0.02 ± 0.002)< β<(0.27 ± 0.04)) with no distinct seasonality. By separating the complete dataset in 10 different ozone regimes, we found that in moderately or less polluted atmospheric conditions the main driving force of sesquiterpene emissions is the temperature, but when ambient ozone mixing ratios exceed a~critical threshold of (36.6 ± 3.9) ppbv, the emissions become primarily correlated with ozone. Considering the complete dataset, cross correlation analysis resulted in highest correlation with ambient ozone mixing ratios (CCO3=0.63 ± 0.01; CCT=0.47 ± 0.02 at t=0 h for temperature) with a time shift 2–4 h prior to the emissions. An only temperature dependent algorithm was found to substantially underestimate the induced emissions (20 % of the measured; R2=0.31). However, the addition of an ozone dependent term improved substantially the fitting between measured and modeled emissions (81 % of the measured; R2=0.63), providing confidence about the reliability of the suggested parameterization for the spruce forest site investigated

Ambient new particle formation parameter indicates potential rise in future events

Atmospheric new particle formation is a general phenomenon observed over coniferous forests. So far nucleation is described as a function of gaseous sulfuric acid concentration only, which is unable to explain the observed seasonality of nucleation events at different measurement sites. Here we introduce a new nucleation parameter including ozone and water vapor concentrations as well as UV-B radiation as a proxy for OH radical formation. Applying this new parameter to field studies conducted at Finnish and German measurement sites it is found capable to predict the occurrence of nucleation events and their seasonal and annual variation indicating a significant role of organics. Extrapolation to possible future conditions of ozone, water vapor and organic concentrations leads to a significant potential increase in nucleation event number

A new parametrization for ambient particle formation over coniferous forests and its potential implications for the future

Atmospheric new particle formation is a general phenomenon observed over coniferous forests. So far nucleation is either parameterised as a function of gaseous sulphuric acid concentration only, which is unable to explain the observed seasonality of nucleation events at different measurement sites, or as a function of sulphuric acid and organic molecules. Here we introduce different nucleation parameters based on the interaction of sulphuric acid and terpene oxidation products and elucidate the individual importance. They include basic trace gas and meteorological measurements such as ozone and water vapour concentrations, temperature (for terpene emission) and UV B radiation as a proxy for OH radical formation. We apply these new parameters to field studies conducted at conducted at Finnish and German measurement sites and compare these to nucleation observations on a daily and annual scale. General agreement was found, although the specific compounds responsible for the nucleation process remain speculative. This can be interpreted as follows: During cooler seasons the emission of biogenic terpenes and the OH availability limits the new particle formation while towards warmer seasons the ratio of ozone and water vapour concentration seems to dominate the general behaviour. Therefore, organics seem to support ambient nucleation besides sulphuric acid or an OH-related compound. Using these nucleation parameters to extrapolate the current conditions to prognosed future concentrations of ozone, water vapour and organic concentrations leads to a significant potential increase in the nucleation event number

Comparison of electron density profiles in the ionosphere from ionospheric assimilations of GPS, CHAMP profiling and ionosondes over Europe

GPS integrated Total Electron Content measurements received at the ground or in space are used for tomographic reconstruction of the ionospheric electron density distribution. The IRI/GCPM model is used as initialisation of the tomographic MART algorithm. During the procedure GPS TEC data are iteratively assimilated to the model. To test the potential of the reconstruction, electron density profiles from IRI/GCPM and the assimilation are compared with ionosonde measurements and CHAMP radio occultation profiles for dates during the HIRAC campaign in April 2001. All profiling methods show electron density values of similar magnitude. It is shown that including TEC GPS data corrects the model towards the ionosonde measurements.Integrale Messungen der Elektronendichte aus GPS-Boden- sowie Radio-Okkultations-Messungen bilden die Datenbasis der hier vorgestellten 3-dimensionalen Tomographie der ionosphärischen Elektronendichteverteilung. Zur Initialisierung des verwendeten iterativen MART Algorithmus wird das IRI/GCPM Modell verwendet, wobei das Modell während der Iteration sukzessiv an die Messdaten angepasst wird. Um das Potential des Verfahrens abzuschätzen, werden Elektronendichteprofile des IRI/GCPM Modells und der Rekonstruktion mit Ionosondenmessungen und CHAMP Okkultationsprofilen verglichen. Dafür wurden Messungen während der HIRAC Kampagne im April 2001 genutzt. Alle hier gezeigten Profilableitungen geben Elektronendichtewerte der selben Größe wieder. Eine Annäherung des IRI/GCPM Modells an die Messwerte der Ionosonde durch die Assimilation der TEC GPS Daten wird gezeigt

Monitoring of a polar plasma convection event with GPS

When L-band radio waves of space based systems such as Global Positioning System (GPS) travel trough the ionosphere and plasmasphere their ray paths are perturbed due to the free electrons. Since the last decade these integrated measurements are used to map the ionosphere for navigational and scientific investigations. In November 2001 a polar plasma convection like ionospheric event has been recognised in vertical TEC maps produced with GPS data. This event on the one hand is shortly compared with the behaviour of the Interplanetary Magnetic Field (IMF) to which it may be related according to former publications. On the other hand the 3-dimensional tomography applying also GPS data is tested on its capability to reconstruct this ionospheric event in the European sector. The different mappings of the two monitoring methods are compared.Wenn L-Band-Radiowellen raumgestützter Navigationssysteme wie das Global Positioning System (GPS) die Ionosphäre oder Plasmasphäre durchlaufen, werden Ihre Strahlwege durch die freien Elektronen verändert. Seit dem letzten Jahrzehnt verwendet man diese integrierten Messungen, um die Ionosphäre im Interesse der Navigation und der Wissenschaft abzubilden. Am Beispiel eines Ereignisses vom November 2001 wurde eine polare Plasmakonvektion in der Ionosphäre durch vertikale TEC –Karten (Total Electron Content), die ebenfalls mit Hilfe von GPS Daten erstellt werden, abgebildet. Einerseits wurde das Ereignis der Plasmakonvektion mit dem Verhalten des Interplanetaren Magnetischen Feldes (IMF) kurz verglichen und auf ihren Zusammenhang hin untersucht. Auf der anderen Seite wurde anhand dieses Ereignisses die Methode einer über den europäischen Raum aufgespannten auf GPS–Daten basierenden 3-dimensionale Tomographie auf ihre Reproduzierbarkeit hin geprüft. Die zwei verschiedenen Methoden des Ionosphärenmonitorings werden verglichen

Ionospheric tomography and first interpretations of including space-based GPS

When L-band radio waves of space-based radio navigation systems such as Global Positioning System (GPS) travel through the atmosphere and ionosphere, their ray paths are bent and their travel time are increased as a result of refractive-index gradients. As the ionosphere is a dispersive medium the two GPS frequencies are subject to different delays in time and modifications in amplitude, phase and polarisation which is an effect of free electrons. By using these two radio frequencies one can derive information about the Total Electron Content integrated along the ray path. After calibration, these data are included into the tomographic reconstruction. The tomographic methode presented in this paper works on algebraic iterative methodes like SART and MART. Calculations are based on International GPS Service (IGS) ground received data. Space-based GPS is provided by LEO (Low Earth Orbiter) satellites like CHAMP. By means of incorporating such occultation data into tomography an improvement of reconstruction of the vertical structure of the electron density is expected. First confirming interpretations of a selected occulation event are presented in this paper. It is shown, that space-based GPS data can improve tomographic results mainly in middle to lower altitudes of the ionosphere.Wenn sich Radiowellen eines Navigationssystemes, wie das des Global Positioning Systems (GPS), in der Atmosphäre und Ionosphäre ausbreiten, erfahren sie eine Beugung des Strahlweges und eine Erhöhung der Laufzeit aufgrund der Gradienten des atmosphärischen Refraktionsindexes. Da die Ionosphäre ein dispersives Medium darstellt, unterliegen beide GPS-Frequenzen dort unterschiedlichen Störungen in Laufzeit und Veränderungen in Amplitude, Phase und Polarisation, was auf die Effekt der freien Elektronen zurückzuführen ist. Unter der Verwendung der beiden Radiofrequenzen kann man Informationen über die Anzahl der über den Strahlweg integrierten Elektronen erhalten. Nach der Kalibrierung dieser Daten, können sie zur tomographischen Rekonstruktion verwendet werden. Die hier vorgestellte Tomographie verwendet algebraisch iterative Methoden, wie SART und MART. Die tomographischen Berechnungen bauen auf bodengestützte GPS-Daten des International GPS Services (IGS) und satellitengestützten GPS-Daten von LEO (Low earth orbiter) Satelliten wie CHAMP auf. Durch die Intergration von Okkultationsdaten in die Tomographie wird eine Verbesserung der Rekonstruktion der vertikalen Struktur der Elektronendichte erwartet. Erste bestätigende Interpretationen eines ausgewählten Okkultationsereignisses werden in diesem Artikel vorgeführt. Es wird gezeigt, dass satellitengestützte GPS-Daten die tomographischen Ergebnisse vorallem in der mittleren und unteren Ionosphäre verbessern können

Nucleation of jet engine oil vapours is a large source of aviation-related ultrafine particles

Large airports are a major source of ultrafine particles, which spread across densely populated residential areas, affecting air quality and human health. Jet engine lubrication oils are detectable in aviation-related ultrafine particles, however, their role in particle formation and growth remains unclear. Here we show the volatility and new-particle-formation ability of a common synthetic jet oil, and the quantified oil fraction in ambient ultrafine particles downwind of Frankfurt International Airport, Germany. We find that the oil mass fraction is largest in the smallest particles (10-18 nm) with 21% on average. Combining ambient particle-phase concentration and volatility of the jet oil compounds, we determine a lower-limit saturation ratio larger than 1 × 105 for ultra-low volatility organic compounds. This indicates that the oil is an efficient nucleation agent. Our results demonstrate that jet oil nucleation is an important mechanism that can explain the abundant observations of high number concentrations of non-refractory ultrafine particles near airports

Islamische Stiftungen zwischen juristischer Norm und sozialer Praxis

Die Bedeutung von Stiftungen für die islamisch geprägten Gesellschaften der Vormoderne lässt sich kaum überschätzen. Stiftungen finanzierten an vielen Orten Einrichtungen der Armen- und Krankenfürsorge, religiöse Institutionen und Aufgaben der kommunalen Infrastruktur, sie dienten aber auch als Grundlage für den Zusammenhalt unterschiedlicher sozialer Gruppen. Heute werden Stiftungen im Rahmen der Debatten zu genuin islamischen Finanzinstrumenten wieder stark diskutiert. In den Beiträgen des Bandes wird die islamische Stiftung nicht als eine statische und unflexible Institution islamischen Rechts verstanden. Vielmehr werden einzelne Stiftungsgeschichten untersucht und in ihrem zeitlichen und regionalen Kontext gesehen. Damit stellen die Autoren die soziale Praxis und die Anpassungsfähigkeit des islamischen Stiftungswesens in den Vordergrund