Messungen von salpetriger Säure und Eispartikeln im Nachlauf von Flugzeugen

Ziel dieser Arbeit war der Aufbau und Einsatz des Atmosphärischen chemischen Ionisations-Massenspektrometers AIMS für boden- und flugzeuggetragene Messungen von salpetriger Säure (HONO). Für das Massenspektrometer wurden eine mit Gleichspannung betriebene Gasentladungsionenquelle und ein spezielles Druckregelventil entwickelt. Während der Instrumentenvergleichskampagne FIONA (Formal Intercomparisons of Observations of Nitrous Acid) an einer Atmosphären-Simulationskammer in Valencia (Spanien) wurde AIMS für HONO kalibriert und erstmals eingesetzt. In verschiedenen Experimenten wurden HONO-Mischungsverhältnisse zwischen 100 pmol/mol und 25 nmol/mol erzeugt und mit AIMS interferenzfrei gemessen. Innerhalb der Messunsicherheit von ±20% stimmen die massenspektrometrischen Messungen gut mit den Methoden der Differenziellen Optischen Absorptions-Spektrometrie und der Long Path Absorption Photometrie überein. Die Massenspektrometrie kann somit zum schnellen und sensitiven Nachweis von HONO in verschmutzter Stadtluft und in Abgasfahnen genutzt werden.rnErste flugzeuggetragene Messungen von HONO mit AIMS wurden 2011 bei der Messkampagne CONCERT (Contrail and Cirrus Experiment) auf dem DLR Forschungsflugzeug Falcon durchgeführt. Hierbei konnte eine Nachweisgrenze von < 10 pmol/mol (3σ, 1s) erreicht werden. Bei Verfolgungsflügen wurden im jungen Abgasstrahl von Passagierflugzeugen molare HONO zu Stickoxid-Verhältnisse (HONO/NO) von 2.0 bis 2.5% gemessen. HONO wird im Triebwerk durch die Reaktion von NO mit OH gebildet. Ein gemessener abnehmender Trend der HONO/NO Verhältnisse mit zunehmendem Stickoxid-Emissionsindex wurde bestätigt und weist auf eine OH Limitierung im jungen Abgasstrahl hin.rnNeben den massenspektrometrischen Messungen wurden Flugzeugmessungen der Partikelsonde Forward Scattering Spectrometer Probe FSSP-300 in jungen Kondensstreifen ausgewertet und analysiert. Aus den gemessenen Partikelgrößenverteilungen wurden Extinktions- und optische Tiefe-Verteilungen abgeleitet und für die Untersuchung verschiedener wissenschaftlicher Fragestellungen, z.B. bezüglich der Partikelform in jungen Kondensstreifen und ihrer Klimawirkung, zur Verfügung gestellt. Im Rahmen dieser Arbeit wurde der Einfluss des Flugzeug- und Triebwerktyps auf mikrophysikalische und optische Eigenschaften von Kondensstreifen untersucht. Unter ähnlichen meteorologischen Bedingungen bezüglich Feuchte, Temperatur und stabiler thermischer Schichtung wurden 2 Minuten alte Kondensstreifen der Passagierflugzeuge vom Typ A319-111, A340-311 und A380-841 verglichen. Im Rahmen der Messunsicherheit wurde keine Änderung des Effektivdurchmessers der Partikelgrößenverteilungen gefunden. Hingegen nehmen mit zunehmendem Flugzeuggewicht die Partikelanzahldichte (162 bis 235 cm-3), die Extinktion (2.1 bis 3.2 km-1), die Absinktiefe des Kondensstreifens (120 bis 290 m) und somit die optische Tiefe der Kondensstreifen (0.25 bis 0.94) zu. Der gemessene Trend wurde durch Vergleich mit zwei unabhängigen Kondensstreifen-Modellen bestätigt. Mit den Messungen wurde eine lineare Abhängigkeit der totalen Extinktion (Extinktion mal Querschnittsfläche des Kondensstreifens) vom Treibstoffverbrauch pro Flugstrecke gefunden und bestätigt.The Atmospheric chemical Ionization Mass Spectrometer (AIMS) was developed for ground based and airborne detection of nitrous acid (HONO). A high voltage gas discharge ion source and a pressure controlling valve were designed and constructed. The instrument was calibrated for HONO in the laboratory. Interferences with respect to water vapor, ozone, and nitric oxide were tested. The AIMS instrument was tested during the instrument intercomparison campaign FIONA (Formal Intercomparisons of Observations of Nitrous Acid) in Valencia (Spain). In the atmospheric simulation chamber different polluted situations with HONO mixing ratios between 100 pmol/mol and 25 nmol/mol were provided. Within the experimental uncertainty of ±20% the mass spectrometric measurements compared well with other methods such as the Differential Optical Absorption technique and the Long Path Absorption Photometric technique. The mass spectrometry proved to be a sensitive and fast method for the detection of HONO in urban plumes or in combustion plumes.rnFirst airborne measurements with AIMS were performed during the Contrail and Cirrus experiment CONCERT with the DLR research aircraft Falcon in 2011. A detection limit for HONO of < 10 pmol/mol (3σ, 1s) was derived. Molar HONO to nitric oxide (HONO/NO) ratios of 2.0 to 2.5% were detected in young exhaust plumes from passenger aircraft. HONO is produced in the engine by the reaction of NO with OH. The observed decrease in the HONO/NO ratio with increasing NO emission indices suggests an OH limitation in the young exhaust plume. OH emission indices of 0.10 to 0.13 g kg-1 were derived.rnIn addition to the mass spectrometric measurements, contrail observations with the forward scattering spectrometer probe FSSP-300 onboard the DLR research aircraft Falcon were evaluated. Extinction and optical depths distributions in young contrails were derived from the particle size distribution in order to analyze the particle shape and the climate impact from young contrails. Within this work the effect of the aircraft and engine type on microphysical and optical contrail properties is investigated. 2 min old contrails from an A319-111, an A340-311 and an A380-841 aircraft were intercompared under similar meteorological conditions in terms of relative humidity, temperature and thermal stratification. The effective diameters of the particle size distributions of the three contrails are similar within the experimental uncertainties. In contrast, the particle number density (162 to 235 cm-3), the extinction (2.1 to 3.2 km-1), the contrail depths (120 to 290 m) and therefore the optical depths (0.25 to 0.94) increase with enhanced aircraft weight. This trend is generally confirmed by model results from two different contrail models. Theoretical considerations provide a base for the observed linear dependence of the total extinction (extinction times contrail cross section) on fuel consumption per flight distance

Contrail ice particle formation in the wakes of airliners - insights from in-situ measurements and modelling

Particle concentrations and trace gas mixing ratios are analyzed, their dilution and their correlations in 2 min old contrails from four airliners of types A319, A340, B737, and A380 under similar meteorological conditions. The results are now published in Geophyscial Research Letters in 2013

Aircraft type influence on contrail properties

The investigation of the impact of aircraft parameters on contrail properties helps to better understand the climate impact from aviation. Yet, in observations, it is a challenge to separate aircraft and meteorological influences on contrail formation. During the CONCERT campaign in November 2008, contrails from 3 Airbus passenger aircraft of type A319-100, A340-300 and A380-800 were probed at cruise under similar meteorological conditions with in-situ instruments on board the DLR research aircraft Falcon

HONO measurements with a chemical ionization mass spectrometer during FIONA

Nitrous acid (HONO) is an important source of the OH radical, the primary oxidant in the atmosphere. The chemistry of HONO and its possible sources in the atmosphere are not well understood. The aims of the FIONA (Formal Intercomparisons of Observations of Nitrous Acid) campaign are to establish a better understanding of HONO chemistry and to intercompare different measurement techniques. Data from 19 instruments from 9 countries including spectroscopy (DOAS, BBCEAS, LIF), wet chemistry, denuders and mass spectrometry were intercompared at typical urban and semi-rural conditions at the simulation chamber Euphore. During the FIONA campaign we deployed an Atmospheric chemical Ionization Mass Spectrometer (AIMS). The AIMS has extensively been calibrated to a gas-phase HONO source and interferences with other gases (particularly water) have been tested. We show first results of our mass spectrometric measurements. For specific observation conditions, the chemical ionization mass spectrometry can be used as a fast and sensitive method for the detection of HONO in the atmosphere

Has the aircraft type an impact on the microphysical parameters of young contrails?

Modeling studies suggest an impact of the aircraft type on the microphysical and optical properties of young contrails. However, up to now, a low intercomparability of meteorological conditions has prevented a study on the aircraft effect on contrail properties using in-situ observations. Therefore, we analyze contrail observations from 3 different aircraft, a large A380, a medium sized A340 and a smaller A319, performed during the CONCERT2008 (CONtrail and Cirrus ExpeRimenT) campaign under similar meteorological conditions in terms of relative humidity over ice (RHi) and wind shear. The young contrails were probed on 19 November 2008 over Northern Germany with instruments onboard the DLR research aircraft Falcon. 1-min old contrails were sampled at an altitude of 10.6 km near ice saturation at temperatures of 217 to 218 K above a natural cirrus cloud layer. We find large differences in the 3 observed contrail optical depth distributions, while the aircraft impact is not as pronounced in the detected particle size spectra. In addition, we simulate the contrail properties from the 3 aircraft with two independent models, the Eulerian particle tracking EULAG-LCM model and the contrail and cirrus prediction tool CoCiP. The models generally confirm the observed trend, an increase in contrail optical depth with increasing aircraft size (or weight). However, the models show smaller contrail optical depths for all aircraft types than observations. These discrepancies are reduced assuming higher values for the ambient relative humidity

Contrail ice particles in aircraft wakes and their climatic importance

Measurements of gaseous (NO, NOy, SO2, HONO) and ice particle concentrations in young contrails in primary and secondary wakes of aircraft of different sizes (B737, A319, A340, A380) are used to investigate ice particle formation behind aircraft. The gas concentrations are largest in the primary wake and decrease with increasing altitude in the secondary wake, as expected for passive trace gases and aircraft-dependent dilution. In contrast, the measured ice particle concentrations were found larger in the secondary wake than in the primary wake. The contrails contain more ice particles than expected for previous black carbon (soot) estimates. The ice concentrations may result from soot induced ice nucleation for a soot number emission index of 10^15 kg^-1. For a doubled ice particle concentration in young contrails, a contrail cirrus model computes about 60% increases of global radiative forcing by contrail cirrus because of simultaneous increases in optical depth, age and cover

In situ measurements of ice saturation in young contrails

Relative humidity with respect to ice (RHi) is a major factor controlling the evolution of aircraft contrails. High-resolution airborne H2O measurements in and near contrails were made at a rate of 4.2 Hz using the novel water vapor mass spectrometer AIMS-H2O with in-flight calibration during the CONtrail, volcano, and Cirrus ExpeRimenT (CONCERT) 2011. Three 2 min old contrails were sampled near 11 km altitude. Independent of the ambient supersaturation or subsaturation over ice, the mean of the RHi frequency distribution within each contrail is shifted toward ice saturation. This shift can be explained by the high ice surface area densities with corresponding RHi relaxation times on the order of 20 s, which lead to the fast equilibration of H2O between the vapor and ice phase. Understanding the interaction of water vapor with ice particles is essential to investigate the life cycle of contrails and cirrus