Tina Jurkat

ACRIDICON–CHUVA Campaign: Studying Tropical Deep Convective Clouds and Precipitation over Amazonia Using the New German Research Aircraft HALO

AbstractBetween 1 September and 4 October 2014, a combined airborne and ground-based measurement campaign was conducted to study tropical deep convective clouds over the Brazilian Amazon rain forest. The new German research aircraft, High Altitude and Long Range Research Aircraft (HALO), a modified Gulfstream G550, and extensive ground-based instrumentation were deployed in and near Manaus (State of Amazonas). The campaign was part of the German–Brazilian Aerosol, Cloud, Precipitation, and Radiation Interactions and Dynamics of Convective Cloud Systems–Cloud Processes of the Main Precipitation Systems in Brazil: A Contribution to Cloud Resolving Modeling and to the GPM (Global Precipitation Measurement) (ACRIDICON– CHUVA) venture to quantify aerosol–cloud–precipitation interactions and their thermodynamic, dynamic, and radiative effects by in situ and remote sensing measurements over Amazonia. The ACRIDICON–CHUVA field observations were carried out in cooperation with the second intensive operating period...

ML-CIRRUS - The airborne experiment on natural cirrus and contrail cirrus with the high-altitude long-range research aircraft HALO

AbstractThe Midlatitude Cirrus experiment (ML-CIRRUS) deployed the High Altitude and Long Range Research Aircraft (HALO) to obtain new insights into nucleation, life cycle, and climate impact of natural cirrus and aircraft-induced contrail cirrus. Direct observations of cirrus properties and their variability are still incomplete, currently limiting our understanding of the clouds’ impact on climate. Also, dynamical effects on clouds and feedbacks are not adequately represented in today’s weather prediction models.Here, we present the rationale, objectives, and selected scientific highlights of ML-CIRRUS using the G-550 aircraft of the German atmospheric science community. The first combined in situ–remote sensing cloud mission with HALO united state-of-the-art cloud probes, a lidar and novel ice residual, aerosol, trace gas, and radiation instrumentation. The aircraft observations were accompanied by remote sensing from satellite and ground and by numerical simulations.In spring 2014, HALO performed 16 f...

Aerosol layers from the 2008 eruptions of Mount Okmok and Mount Kasatochi: In situ upper troposphere and lower stratosphere measurements of sulfate and organics over Europe

In 2008 Mt. Okmok and Mt. Kasatochi started erupting on 12 July and 7 August, respectively, in the Aleutians, depositing emissions of trace gases and aerosols as high as 15.2 km into the atmosphere. During an aircraft campaign, conducted over Europe in October/November 2008, the volcanic aerosol was measured by an Aerodyne Aerosol Mass Spectrometer (AMS), capable of particle chemical composition measurements covering a size diameter range between 40 nm and 1 µm. In the volcanic aerosol layer enhanced submicron particulate sulfate concentrations of up to 2.0 µg m-3 standard temperature and pressure (STP) were observed between 8 and 12 km altitude while background values did not exceed 0.5 µg m-3 (STP). 21 % of the volcanic aerosol consisted of carbonaceous material that increased by a factor of 1.9 in mass compared to the free troposphere. Enhanced gaseous sulfur dioxide concentrations measured by an ion trap chemical ionization mass spectrometer (IT-CIMS) of up to 1.3 µg m-3 were encountered. An onboard radiation measurement system simultaneously detected an enhanced aerosol signal. Furthermore, two German lidar stations identified an aerosol layer before and after the campaign. Data analysis shows that the aerosol layer was observed mainly in the lowermost stratosphere. Correlation of particulate sulfate concentration and sulfur dioxide mixing ratios indicate that after 3 month residence time in the stratosphere not all sulfur dioxide has been converted into sulfate aerosol. The significant fraction of organic material might have implications on heterogeneous chemistry in the stratosphere which need to be explored more thoroughly

Biofuel blending reduces particle emissions from aircraft engines at cruise conditions

Aviation-related aerosol emissions contribute to the formation of contrail cirrus clouds that can alter upper tropospheric radiation and water budgets, and therefore climate. The magnitude of air-traffic-related aerosol–cloud interactions and the ways in which these interactions might change in the future remain uncertain. Modelling studies of the present and future effects of aviation on climate require detailed information about the number of aerosol particles emitted per kilogram of fuel burned and the microphysical properties of those aerosols that are relevant for cloud formation. However, previous observational data at cruise altitudes are sparse for engines burning conventional fuels, and no data have previously been reported for biofuel use in-flight. Here we report observations from research aircraft that sampled the exhaust of engines onboard a NASA DC‐8 aircraft as they burned conventional Jet A fuel and a 50:50 (by volume) blend of Jet A fuel and a biofuel derived from Camelina oil. We show that, compared to using conventional fuels, biofuel blending reduces particle number and mass emissions immediately behind the aircraft by 50 to 70 per cent. Our observations quantify the impact of biofuel blending on aerosol emissions at cruise conditions and provide key microphysical parameters, which will be useful to assess the potential of biofuel use in aviation as a viable strategy to mitigate climate change.

Evolution of CO2, SO2, HCl, and HNO3 in the volcanic plumes from Etna

The volcanic plumes from degassing Etna (Italy) were extensively probed with instruments onboard the Deutsches Zentrum fur Luft- und Raumfahrt research aircraft Falcon during the contrail, volcano, and cirrus experiment CONCERT on 29/30 September 2011. Up to 10.4 ppmv SO2 and 0.3 ppmv HCl were detected with the atmospheric chemical ionization mass spectrometer AIMS at 3.1 km altitude and 20 km distance to the summit. HNO3 is the dominant reactive nitrogen component in the plumes. Linking aircraft and ground-based observations by Hybrid Single-Particle Lagrangian Integrated Trajectory dispersion modeling, we identify two crater plumes with different compositions primarily injected by the Bocca Nuova and North East craters. Uniquely, we follow their chemical evolution up to 5 h plume age. Our results show that CO2/SO2 and SO2/HCl molar ratios are stable in the ageing plumes. Hence, conversion of SO2 to H2SO4 and partitioning of HCl in acidic plume particles play a minor role at dry tropospheric conditions. Thus, these trace gases allow monitoring volcanic activity far from the crater.

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.

Quasi-Spherical Ice in Convective Clouds

AbstractHomogeneous freezing of supercooled droplets occurs in convective systems in low and midlatitudes. This droplet-freezing process leads to the formation of a large amount of small ice particles, so-called frozen droplets, that are transported to the upper parts of anvil outflows, where they can influence the cloud radiative properties. However, the detailed microphysics and, thus, the scattering properties of these small ice particles are highly uncertain. Here, the link between the microphysical and optical properties of frozen droplets is investigated in cloud chamber experiments, where the frozen droplets were formed, grown, and sublimated under controlled conditions. It was found that frozen droplets developed a high degree of small-scale complexity after their initial formation and subsequent growth. During sublimation, the small-scale complexity disappeared, releasing a smooth and near-spherical ice particle. Angular light scattering and depolarization measurements confirmed that these sublim...

A quantitative analysis of stratospheric HCl, HNO3, and O3 in the tropopause region near the subtropical jet

The effects of chemical two-way mixing on the Extratropical Transition Layer (ExTL) near the subtropical jet are investigated by stratospheric tracer-tracer correlations. To this end, in situ measurements were performed west of Africa (25-32 ◦ N) during the Transport and Composition of the Upper Troposphere Lower Stratosphere (UTLS)/Earth System Model Validation (TACTS/ESMVal) mission in August/September 2012. The Atmospheric chemical Ionization Mass Spectrometer sampling HCl and HNO3 was for the first time deployed on the new German High Altitude and Long range research aircraft (HALO). Measurements of O3, CO, European Centre for Medium-Range Weather Forecasts (ECMWF) analysis, and the tight correlation of the unambiguous tracer HCl to O3 and HNO3 in the lower stratosphere were used to quantify the stratospheric content of these species in the ExTL. With increasing distance from the tropopause, the stratospheric content increased from 10% to 100% with differing profiles for HNO 3 and O 3 . Tropospheric fractions of 20% HNO 3 and 40% O 3 were detected up to a distance of 30 K above the tropopause.

Reply to comment from Liotta and Rizzo on “Evolution of CO2 , SO2 , HCl and HNO3 in the volcanic plumes from Etna” by Voigt et al. [Geophys. Res. Lett.; 41, doi:10.1002/2013GL058974]

Editor’s Note: The following comment and reply arise from an article published in Geophysical Research Letters by Voigt et al. (2014). The article addresses a volcanology topic, and the commenters take issue with some conclusions and offer an analysis of their own. Voigt and co-authors have responded. Why is this comment-and-reply being published in the Bulletin? It is because Geophysical Research Letters is one of a number of journals that do not offer any published forum for discussion of the papers they publish. This is a matter of editorial policy and a decision for each journal. The Bulletin of Volcanology does provide a forum for discussion of articles published. When contacted by Marcello Liotta with the request that the Bulletin consider hosting a discussion of the Voigt et al. volcanology article in GRL, I agreed to do so if the GRL authors were willing to engage with the comment. Voigt and co-authors were willing to do so and have been allowed a small amount of additional space to summarize for Bulletin readers the key points of the GRL paper under discussion before responding directly to the comment from Liotta and Rizzo. I hope that Bulletin readers find the discussion and reply of interest.

Aircraft Emissions at Cruise and Plume Processes

The detection of aircraft emissions at cruise altitudes helps to understand and assess the effects of aviation on atmospheric composition and climate. Since the early 1990s, aircraft emissions of carbon dioxide, water vapor, nitrogen and sulfur oxides, aerosol and soot and their processing in the atmosphere as well as contrail formation have been measured in situ with the instrumented DLR research aircraft Falcon. Scientific results from a series of aircraft missions are summarized and explained, uncertainties are discussed and suggestions are made on how to move forward.