The Pagami Creek smoke plume after long-range transport to the upper troposphere over Europe – aerosol properties and black carbon mixing state

During the CONCERT 2011 field experiment with the DLR research aircraft Falcon, an enhanced aerosol layer with particle linear depolarization ratios of 6–8% at 532 nm was observed at altitudes above 10 km over northeast Germany on 16 September 2011. Dispersion simulations with HYSPILT suggest that the elevated aerosol layer originated from the Pagami Creek forest fire in Minnesota, USA, which caused pyro-convective uplift of particles and gases. The 3–4 day-old smoke plume had high total refractory black carbon (rBC) mass concentrations of 0.03–0.35 μg m⁻³ at standard temperature and pressure (STP) with rBC mass equivalent diameter predominantly smaller than 130 nm. Assuming a core-shell particle structure, the BC cores exhibit very thick (median: 105–136 nm) BC-free coatings. A large fraction of the BC-containing particles disintegrated into a BC-free fragment and a BC fragment while passing through the laser beam of the Single Particle Soot Photometer (SP2). In this study, the disintegration is a result of very thick coatings around the BC cores. This is in contrast to a previous study in a forest-fire plume, where it was hypothesized to be a result of BC cores being attached to a BC-free particle. For the high-altitude forest-fire aerosol layer observed in this study, increased mass specific light-absorption cross sections of BC can be expected due to the very thick coatings around the BC cores, while this would not be the case for the attached-type morphology. We estimate the BC mass import from the Pagami Creek forest fire into the upper troposphere/lower stratosphere (UTLS) region (best estimate: 25 Mg rBC). A comparison to black carbon emission rates from aviation underlines the importance of pyro-convection on the BC load in the UTLS region. Our study provides detailed information on the microphysics and the mixing state of BC in the forest-fire aerosol layer in the upper troposphere that can be used to better understand and investigate the radiative impact of such upper tropospheric aerosol layers

The Pagami Creek smoke plume after long-range transport to the upper troposphere over Europe – Aerosol properties and black carbon mixing state

During the CONCERT 2011 field experiment with the DLR research aircraft Falcon, an enhanced aerosol layer with particle linear depolarization ratios of 6–8% at 532 nm was observed at altitudes above 10 km over northeast Germany on 16 September 2011. Dispersion simulations with HYSPILT suggest that the elevated aerosol layer originated from the Pagami Creek forest fire in Minnesota, USA, which caused pyro-convective uplift of particles and gases. The 3–4 day-old smoke plume had high total refractory black carbon (rBC) mass concentrations of 0.03–0.35 μg m−3 at standard temperature and pressure (STP) with rBC mass equivalent diameter predominantly smaller than 130 nm. Assuming a core-shell particle structure, the BC cores exhibit very thick (median: 105–136 nm) BC-free coatings. A large fraction of the BC-containing particles disintegrated into a BC-free fragment and a BC fragment while passing through the laser beam of the Single Particle Soot Photometer (SP2). In this study, the disintegration is a result of very thick coatings around the BC cores. This is in contrast to a previous study in a forest-fire plume, where it was hypothesized to be a result of BC cores being attached to a BC-free particle. For the high-altitude forest-fire aerosol layer observed in this study, increased mass specific light-absorption cross sections of BC can be expected due to the very thick coatings around the BC cores, while this would not be the case for the attached-type morphology. We estimate the BC mass import from the Pagami Creek forest fire into the upper troposphere/lower stratosphere (UTLS) region (best estimate: 25 Mg rBC). A comparison to black carbon emission rates from aviation underlines the importance of pyro-convection on the BC load in the UTLS region. Our study provides detailed information on the microphysics and the mixing state of BC in the forest-fire aerosol layer in the upper troposphere that can be used to better understand and investigate the radiative impact of such upper tropospheric aerosol layers

Stratospheric aerosol - Observations, processes, and impact on climate

Interest in stratospheric aerosol and its role in climate have increased over the last decade due to the observed increase in stratospheric aerosol since 2000 and the potential for changes in the sulfur cycle induced by climate change. This review provides an overview about the advances in stratospheric aerosol research since the last comprehensive assessment of stratospheric aerosol was published in 2006. A crucial development since 2006 is the substantial improvement in the agreement between in situ and space-based inferences of stratospheric aerosol properties during volcanically quiescent periods. Furthermore, new measurement systems and techniques, both in situ and space based, have been developed for measuring physical aerosol properties with greater accuracy and for characterizing aerosol composition. However, these changes induce challenges to constructing a long-term stratospheric aerosol climatology. Currently, changes in stratospheric aerosol levels less than 20% cannot be confidently quantified. The volcanic signals tend to mask any nonvolcanically driven change, making them difficult to understand. While the role of carbonyl sulfide as a substantial and relatively constant source of stratospheric sulfur has been confirmed by new observations and model simulations, large uncertainties remain with respect to the contribution from anthropogenic sulfur dioxide emissions. New evidence has been provided that stratospheric aerosol can also contain small amounts of nonsulfate matter such as black carbon and organics. Chemistry-climate models have substantially increased in quantity and sophistication. In many models the implementation of stratospheric aerosol processes is coupled to radiation and/or stratospheric chemistry modules to account for relevant feedback processes

Solutions for the size & concentration measurement of aerosols from combustion

Currently the main pollution comes from the anthropogenic sources related to residential heating and combustion. Most of the emitted particles from this sources are in the mode below 1 μm. Therefore, only by using methods based on the electric mobility separation and size enhancement we can measure the size and concentration of this particles from nano to ultrafine sizes. This contribution describes the most recent methods how to study particle size and concentration of the particles coming from combustion sources

Solutions for the size & concentration measurement of aerosols from combustion

Currently the main pollution comes from the anthropogenic sources related to residential heating and combustion. Most of the emitted particles from this sources are in the mode below 1 μm. Therefore, only by using methods based on the electric mobility separation and size enhancement we can measure the size and concentration of this particles from nano to ultrafine sizes. This contribution describes the most recent methods how to study particle size and concentration of the particles coming from combustion sources

On the visibility of airborne volcanic ash and mineral dust from the pilot’s perspective in flight

In April 2010, volcanic ash from the Eyjafjalla volcano in Iceland strongly impacted aviation in Europe. In order to prevent a similar scenario in the future, a threshold value for safe aviation based on actual mass concentrations was introduced (2 mg m3 in Germany). This study contrasts microphysical and optical properties of volcanic ash and mineral dust and assesses the detectability of potentially dangerous ash layers (mass concentration larger than 2 mg m3) from a pilot’s perspective during a flight. Also the possibility to distinguish between volcanic ash and other aerosols is investigated. The visual detectability of airborne volcanic ash is addressed based on idealized radiative transfer simulations and on airborne observations with the DLR Falcon gathered during the Eyjafjalla volcanic ash research flights in 2010 and during the Saharan Mineral Dust Experiments in 2006 and 2008. Mineral dust and volcanic ash aerosol both show an enhanced coarse mode (>1 lm) aerosol concentration, but volcanic ash aerosol additionally contains a significant number of Aitken mode particles (<150 nm) not present in mineral dust. Under daylight clear-sky conditions and depending on the viewing geometry, volcanic ash is visible already at mass concentrations far below what is currently considered dangerous for aircraft engines. However, it is not possible to visually distinguish volcanic ash from other aerosol layers or to determine whether a volcanic ash layer is potentially dangerous (mass concentration larger or smaller than 2mgm3). Different appearances due to microphysical differences of both aerosol types are not detectable by the human eye. Nonetheless, as ash concentrations can vary significantly over distances travelled by an airplane within seconds, this visual threat evaluation may contribute greatly to the short-term response of pilots in ash-contaminated air space

Volcanic Ash Layers of the Eyjafjalla over Europe in April/May 2010 - Characterized by the DLR-Falcon Aircraft and by Ground-based Lidars

In April/May 2010 large areas of the European airspace were impacted by volcanic ash layers originating from the Eyjafjalla volcano in Iceland. Between 19 April and 18 May 2010, the DLR-Falcon performed 17 research flights in aged (up to 120 h) volcanic ash plumes over Central and Western Europe, but also in a young (7 h) plume close to the volcano in Iceland. The Falcon was instrumented with a downward looking, scanning 2-μm-Wind-Lidar (aerosol backscattering and horizontal wind, 100 m vertical resolution), and several in situ instruments. The aerosol in situ instrumentation, including wing station probes (PCASP, FSSP-300, 2D-C), covered particle number, size, and chemical composition in the size range between 5 nm and 800 μm. Further in situ instruments measured O3, CO, SO2, H2O, and standard meteorological parameters. When possible, the flight path of the Falcon was directed to pass over various ground-based lidar stations like Munich-Maisach, Leipzig, Hamburg, Stuttgart, Jülich, and Cabauw. Volcanic ash layers were detected at altitudes between 1 and 6 km. The layers had a depth between 0.1 and 3 km and spread several 100 km in the horizontal. Sometimes the volcanic ash plumes showed a multi-layer structure. Altogether 35 flight legs were identified, when the Falcon was inside a volcanic ash plume. The maximum ash mass concentrations and SO2 mixing ratios measured in the young plume were about 1 mg m-3 and 150 nmol mol-1, respectively. The chemical composition of single particles was derived by means of scanning electron microscopy from impaction samples. Particles were mainly composed of secondary sulphate and silicate minerals and showed a crystalline structure. Volcanic glass was not present in the samples investigated. The element chemical composition of the particles was used to constrain the complex index of refraction, which is important for the derivation of the particle size distribution from optical particle counters. In this talk, we give a short overview of the DLR-Falcon research flights in April/May 2010. We show synergies between the combination of ground-based and airborne measurements, and focus on an intercomparison of the airborne data with measurements of the EARLINET lidars at Munich-Maisach (48.21°N, 11.26°E) and Leipzig (51.35°N, 12.44°E). Uncertainties in the derived mass concentration arising from the uncertainty in the imaginary part of the refractive index will be discussed