Evidence for heterogeneous chlorine activation in the tropical UTLS

Airborne in-situ observations of ClO in the tropics were made during the TROCCINOX (Aracatuba, Brazil, February 2005) and SCOUT-O<sub>3</sub> (Darwin, Australia, November/December 2005) field campaigns. While during most flights significant amounts of ClO (≈10–20 parts per trillion, ppt) were present only in aged stratospheric air, instances of enhanced ClO mixing ratios of up to 40 ppt – significantly exceeding those expected from gas phase chemistry – were observed in air masses of a more tropospheric character. Most of these observations are associated with low temperatures or with the presence of cirrus clouds (often both), suggesting that cirrus ice particles and/or liquid …

Comparing airborne and satellite retrievals of cloud optical thickness and particle effective radius using a spectral radiance ratio technique: two case studies for cirrus and deep convective clouds

Solar radiation reflected by cirrus and deep convective clouds (DCCs) was measured by the Spectral Modular Airborne Radiation Measurement System (SMART) installed on the German High Altitude and Long Range Research Aircraft (HALO) during the Mid-Latitude Cirrus (ML-CIRRUS) and the Aerosol, Cloud, Precipitation, and Radiation Interaction and Dynamic of Convective Clouds System – Cloud Processes of the Main Precipitation Systems in Brazil: A Contribution to Cloud Resolving Modelling and to the Global Precipitation Measurement (ACRIDICON-CHUVA) campaigns. On particular flights, HALO performed measurements closely collocated with overpasses of the Moderate Resolution Imaging Spectroradiometer (…

A new airborne tandem platform for collocated measurements of microphysical cloud and radiation properties

Abstract. A new airborne tandem measurement platform for cloud-radiation interaction studies is introduced in this paper. It consists of a Learjet 35A research aircraft and the AIRcraft TOwed Sensor Shuttle (AIRTOSS), which is an instrumented drag-body towed by the Learjet. Currently, the AIRTOSS is instrumented with a Cloud Imaging Probe (CIP) for measuring cloud microphysical properties and an Inertial Navigation System (INS) for measurements of flight attitudes. The cable dragging AIRTOSS can be as long as four kilometres. Thus, truly collocated measurements in two altitudes above, in, and below clouds can be obtained. Results from first test flights with Learjet and AIRTOSS are reported…

Atmospheric radiative effects of an in-situ measured Saharan dust plume and the role of large particles

This work will present aerosol size distributions measured in a Saharan dust plume between 0.9 and 12 km altitude during the ACE-2 campaign 1997. The distributions contain a significant fraction of large particles of diameters from 4 to 30 μm. Radiative transfer calculations have been performed using these data as input. Shortwave, longwave as well as total atmospheric radiative effects (AREs) of the dust plume are investigated over ocean and desert within the scope of sensitivity studies considering varied input parameters like solar zenith angle, scaled total dust optical depth, tropospheric standard aerosol profiles and particle complex refractive index. The results indicate that the lar…

Cloud droplets to drizzle: Contribution of transition drops to microphysical and optical properties of marine stratocumulus clouds

Aircraft measurements of the ubiquitous marine stratocumulus cloud type, with over 3000 km of in situ data from the Pacific during the Cloud System Evolution in the Trades experiment, show the ability of the Holographic Detector for Clouds (HOLODEC) instrument to smoothly interpolate the small and large droplet data collected with Cloud Droplet Probe and 2DC instruments. The combined, comprehensive instrument suite reveals a surprisingly large contribution in the predrizzle size range of 40–80 μm (transition droplets, or drizzlets), a range typically not measured and assumed to reside in a condensation-to-collision minimum between cloud droplet and drizzle modes. Besides shedding light on t…

Application Of Microholography for Ground-based In Situ Measurements in Stratus Cloud Layers: A Case Study

Abstract A holographic droplet and aerosol recording system (HODAR) has been designed and operated in situ in a low-level stratus cloud layer adopting the Fraunhofer in-line technique to measure sizes and velocity vectors of cloud droplets as well as to determine sizes and shapes of other hydrometeors (e.g., graupel). The particle-size radii covered by this ground-based instrument range from three to several hundred micrometers. A case study conducted on the Kleiner Feldberg Mountain Observatory near Frankfurt, Germany, during November 1990 documents the temporal evolution of the cloud-droplet size distribution over a period of 19 h during which the size distribution changed from monomodal …

Microphysical Properties of Ice Crystal Precipitation and Surface-Generated Ice Crystals in a High Alpine Environment in Switzerland

AbstractDuring the Cloud and Aerosol Characterization Experiment (CLACE) 2013 field campaign at the High Altitude Research Station Jungfraujoch, Switzerland, optically thin pure ice clouds and ice crystal precipitation were measured using holographic and other in situ particle instruments. For cloud particles, particle images, positions in space, concentrations, and size distributions were obtained, allowing one to extract size distributions classified by ice crystal habit. Small ice crystals occurring under conditions with a vertically thin cloud layer above and a stratocumulus layer approximately 1 km below exhibit similar properties in size and crystal habits as Antarctic/Arctic diamond …

Riming of Graupel: Wind Tunnel Investigations of Collection Kernels and Growth Regimes

Abstract Laboratory experiments were carried out in the vertical wind tunnel in Mainz, Germany, to study the collision coalescence growth of single spherical ice particles having initial radii between 290 and 380 μm while they were freely floated in a laminar flow containing a cloud of supercooled droplets with radii between 10 and 20 μm. The experiments were performed in a temperature range between −8 and −12°C, where riming proceeds in the atmosphere, and with cloud liquid water contents lying between 0.9 and 1.6 g m−3 (i.e., values typically found in mixed-phase clouds). The collection kernels were calculated from the mass increase of the rimed ice particles and the average liquid water …

Chemical analysis of refractory stratospheric aerosol particles collected within the arctic vortex and inside polar stratospheric clouds

Abstract. Stratospheric aerosol particles with diameters larger than about 10 nm were collected within the arctic vortex during two polar flight campaigns: RECONCILE in winter 2010 and ESSenCe in winter 2011. Impactors were installed on board the aircraft M-55 Geophysica, which was operated from Kiruna, Sweden. Flights were performed at a height of up to 21 km and some of the particle samples were taken within distinct polar stratospheric clouds (PSCs). The chemical composition, size and morphology of refractory particles were analyzed by scanning electron microscopy and energy-dispersive X-ray microanalysis. During ESSenCe no refractory particles with diameters above 500 nm were sampled. I…

On the occurrence of ClO in cirrus clouds and volcanic aerosol in the tropopause region

Airborne observations during descents of the ER-2 through layers of volcanic aerosol (Mount Pinatubo eruption of 1991) and a cirrus cloud are utilized to study the the abundance of ClO and its relation to aerosol surface area in the midlatitude tropopause region. During a cirrus event near the tropopause ClO mixing ratios up to 2.7 pptv were detected and near the tropopause ClO levels from a few to 70 pptv were found. These measurements are associated with large experimental uncertainties but demonstrate the possible presence of ClO inside cirrus clouds and near the tropopause. Model calculations show that possible enhancements of ClO by heterogeneous chemistry on cirrus cloud particles cou…

Clouds and aerosols in Puerto Rico - a new evaluation

The influence of aerosols, both natural and anthropogenic, remains a major area of uncertainty when predicting the properties and behaviour of clouds and their influence on climate. In an attempt to better understand warm cloud formation in a tropical marine environment, a period of intensive measurements took place in December 2004 in Puerto Rico, using some of the latest developments in online instrumentation such as aerosol mass spectrometers, cloud condensation nuclei counters and a hygroscopicity tandem differential mobility analyser. Simultaneous online measurements of aerosol size distributions, composition, hygroscopicity and optical properties were made near the lighthouse of Cape …

Ultrathin Tropical Tropopause Clouds (UTTCs): II. Stabilization mechanisms

Abstract. Mechanisms by which subvisible cirrus clouds (SVCs) might contribute to dehydration close to the tropical tropopause are not well understood. Recently Ultrathin Tropical Tropopause Clouds (UTTCs) with optical depths around 10-4 have been detected in the western Indian ocean. These clouds cover thousands of square kilometers as 200-300 m thick distinct and homogeneous layer just below the tropical tropopause. In their condensed phase UTTCs contain only 1-5% of the total water, and essentially no nitric acid. A new cloud stabilization mechanism is required to explain this small fraction of the condensed water content in the clouds and their small vertical thickness. This work sugges…

In Situ, Airborne Instrumentation: Addressing and Solving Measurement Problems in Ice Clouds

The workshop on in situ airborne instrumentation: addressing and solving measurement problems in ice clouds, June 25-27, 2010, Oregon, aimed to identify unresolved questions concerning ice formation and evolution in ice clouds, assess the current state of instrumentation that can address these problems, introduce emerging technology that may overcome current measurement issues, and recommend future courses of action to improve our understanding of ice cloud microphysical. Eleven presentations were made covering measurement challenges associated measuring the composition and concentration of all the modes of ice nuclei (IN), measuring the morphology, mass, surface, and optical properties of …

Comparing Airborne and Satellite Retrievals of Optical and Microphysical Properties of Cirrus and Deep Convective Clouds using a Radiance Ratio Technique

Abstract. Solar radiation reflected by cirrus and deep convective clouds (DCCs) was measured by the Spectral Modular Airborne Radiation Measurement System (SMART) installed on the German HALO (High Altitude and Long Range Research Aircraft) during the ML-CIRRUS and the ACRIDICON-CHUVA campaigns. In particular flights, HALO performed closely collocated measurements with overpasses of the Moderate Resolution Imaging Spectroradiometer (MODIS) on board of Aqua satellite. Based on the nadir upward radiance, the optical thickness τ and bulk particle effective radius reff of cirrus and DCC are retrieved using a radiance ratio algorithm which considers the cloud thermodynamic phase, the cloud verti…

In situ observations of new particle formation in the tropical upper troposphere: the role of clouds and the nucleation mechanism

New particle formation (NPF), which generates nucleation mode aerosol, was observed in the tropical Upper Troposphere (UT) and Tropical Tropopause Layer (TTL) by in situ airborne measurements over South America (January–March 2005), Australia (November–December 2005), West Africa (August 2006) and Central America (2004–2007). Particularly intense NPF was found at the bottom of the TTL. Measurements with a set of condensation particle counters (CPCs) with different <i>d</i><sub>p50</sub> (50% lower size detection efficiency diameter or "cut-off diameter") were conducted on board the M-55 <i>Geophysica</i> in the altitude range of 12.0–20.5 km and on board …

Drop Shapes and Axis Ratio Distributions: Comparison between 2D Video Disdrometer and Wind-Tunnel Measurements

Abstract Comparisons of drop shapes between measurements made using 2D video disdrometer (2DVD) and wind-tunnel experiments are presented. Comparisons are made in terms of the mean drop shapes and the axis ratio distributions. Very close agreement of the mean shapes is seen between the two sets of measurements; the same applies to the mean axis ratio versus drop diameter. Also, in both sets of measurements, an increase in the oscillation amplitudes with increasing drop diameter is observed. In the case of the 2DVD, a small increase in the skewness was also detected. Given that the two sets of measurements were conducted in very different conditions, the agreement between the two sets of dat…

The ACRIDICON-CHUVA campaign: Studying tropical deep convective clouds and precipitation over Amazonia using the new German research aircraft HALO

Abstract Between 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 Precipitatio…

The realization of autonomous, aircraft-based, real-time aerosol mass spectrometry in the upper troposphere and lower stratosphere

Abstract. We report on the developments that enabled the field deployment of a fully-automated aerosol mass spectrometer, specially designed for high-altitude measurements on unpressurised aircraft. The merits of the two main categories of real-time aerosol mass spectrometry, i.e. (a) single particle laser desorption and ionization, and (b) continuous thermal desorption / electron impact ionization of aerosols, have been integrated into one compact apparatus with the aim to perform in-situ real-time analysis of aerosol chemical composition. The demonstrated instrument, named ERICA (European Research council Instrument for the Chemical composition of Aerosols), operated successfully aboard t…

Comparison of Two Aerodynamic Lenses as an Inlet for a Single Particle Laser Ablation Mass Spectrometer

By means of a newly designed portable aerosol mass spectrometer SPLAT (Single Particle Laser Ablation Time-of-flight mass spectrometer) for the analysis of single atmospheric aerosol particles we investigated the system performance in dependency on two different aerodynamic lenses (Liu and Schreiner type) capable of focusing particles with diameters ranging from 80 nm to 800 nm and 300 nm to 3000 nm, respectively. By using the pressure regulated Schreiner lens, the instrument is independent of variations in atmospheric pressure which would lead to changing dynamical properties of the aerosol particles. Active pressure control inside the inlet system facilitates airborne measurements without…

Aerosol filtration efficiency of household materials for homemade face masks: Influence of material properties, particle size, particle electrical charge, face velocity, and leaks

As a consequence of the COVID-19 pandemic caused by the SARS-CoV-2 virus, the widespread daily use of face masks is promoted worldwide. Particle-size dependent filtration efficiencies (FE; dp = 30 nm–10 µm), applying a particle counting approach, and additionally pressure drops (Δp) were determined for 44 samples of household materials and several medical masks. Huge FE differences were found between sample materials and for different particle sizes, spanning from <10% up to almost 100%. Minimum FE were determined for dp = 50–500 nm particles with significantly larger values for dp = 30 nm particles and especially for those with dp > 2.5 µm. Measurements at different numbers of layers…

Enhancements of the refractory submicron aerosol fraction in the Arctic polar vortex: feature or exception ?

In situ measurements with a four-channel stratospheric condensation particle counter (CPC) were conducted at up to 20 km altitude on board the aircraft M-55 Geophysica from Kiruna, Sweden, in January through March (EUPLEX 2003, RECONCILE 2010) and in December (ESSenCe 2011). During all campaigns air masses from the upper stratosphere and mesosphere were subsiding inside the Arctic winter vortex, thus initializing a transport of refractory aerosol into the lower stratosphere (Θ 3 were generally detected. Up to 8 of these 11 particles per cm3 were found to contain thermo-stable (at 250 °C) residuals with diameters of 10 nm to about 1 μm. Particle mixing ratios (150 mg−1) and fractions of non-…

In situ detection of stratosphere-troposphere exchange of cirrus particles in the midlatitudes

Airborne trace gas, microphysical, and radiation measurements were performed during the AIRcraft TOwed Sensor Shuttle - Inhomogeneous Cirrus Experiment over northern Germany in 2013. Based on high-precision nitrous oxide (N2O) and carbon monoxide (CO) in situ data, stratospheric air could be identified, which contained cirrus cloud particles. Consistent with the stratospheric N2O data, backward trajectories indicate that the sampled air masses crossed the dynamical tropopause in the last 3 h before the measurement. These air masses contained cirrus particles, which were formed during slow ascent in the troposphere and subsequently mixed with stratospheric air. From the CO-N2O correlation th…

Nitric acid trihydrate nucleation and denitrification in the Arctic stratosphere

Abstract. Nitric acid trihydrate (NAT) particles in the polar stratosphere have been shown to be responsible for vertical redistribution of reactive nitrogen (NOy). Recent observations by Cloud–Aerosol Lidar with Orthogonal Polarization (CALIOP) aboard the CALIPSO satellite have been explained in terms of heterogeneous nucleation of NAT on foreign nuclei, revealing this to be an important formation pathway for the NAT particles. In state of the art global- or regional-scale models, heterogeneous NAT nucleation is currently simulated in a very coarse manner using a constant, saturation-independent nucleation rate. Here we present first simulations for the Arctic winter 2009/2010 applying a n…

Penetration efficiency of nanometer-sized aerosol particles in tubes under turbulent flow conditions

Abstract In order to quantify losses of nanometer-sized particles in turbulent flows through tubes, their penetration efficiencies were measured as a function of the particle size, Stokes number and Reynolds number. The penetration efficiency of tungsten oxide and ammonium nitrate particles with diameters between 3 and 17 nm was investigated in turbulent flow conditions with Reynolds numbers (Re) extending from 4500 to 10,500. The measured penetration efficiencies in straight tubes were found to deviate from the empirical correlation of Lee and Gieseke (1994) . In contrast, the empirical equation of Fan and Ahmadi (1993) agrees better with our experimental results, also in comparison with t…

Application of an O-ring pinch device as a constant-pressure inlet (CPI) for airborne sampling

We present a novel and compact design of a constant-pressure inlet (CPI) developed for use in airborne aerosol mass spectrometry. In particular, the inlet system is optimized for aerodynamic lenses commonly used in aerosol mass spectrometers, in which efficient focusing of aerosol particles into a vacuum chamber requires a precisely controlled lens pressure, typically of a few hectopascals. The CPI device can also be used in condensation particle counters (CPCs), cloud condensation nucleus counters (CCNCs), and gas-phase sampling instruments across a wide range of altitudes and inlet pressures. The constant pressure is achieved by changing the inner diameter of a properly scaled O-ring that…

Size Matters More Than Chemistry for Cloud-Nucleating Ability of Aerosol Particles

Size-resolved cloud condensation nuclei (CCN) spectra measured for various aerosol types at a non-urban site in Germany showed that CCN concentrations are mainly determined by the aerosol number size distribution. Distinct variations of CCN activation with particle chemical composition were observed but played a secondary role. When the temporal variation of chemical effects on CCN activation is neglected, variation in the size distribution alone explains 84 to 96% of the variation in CCN concentrations. Understanding that particles' ability to act as CCN is largely controlled by aerosol size rather than composition greatly facilitates the treatment of aerosol effects on cloud physics in re…

Inadvertent climate modification due to anthropogenic lead

Atmospheric particles are thought to initiate the majority of terrestrial precipitation. Field-based measurements of ice-crystal residues, together with controlled environment experiments on artificial clouds, suggest that anthropogenic lead-containing particles are among the most efficient ice-forming substances in the atmosphere.

Airborne measurements of the nitric acid partitioning in persistent contrails

This study reports the first systematic measurements of nitric acid (HNO3) uptake in contrail ice particles at typical aircraft cruise altitudes. During the CIRRUS-III campaign cirrus clouds and almost 40 persistent contrails were probed with in situ instruments over Germany and Northern Europe in November 2006. Besides reactive nitrogen, water vapor, cloud ice water content, ice particle size distributions, and condensation nuclei were measured during 6 flights. Contrails with ages up to 12 h were detected at altitudes 10–11.5 km and temperatures 211–220 K. These contrails had a larger ice phase fraction of total nitric acid (HNO3ice/HNO3tot = 6%) than the ambient cirrus layers (3%). On av…

Shapes and oscillations of raindrops with reduced surface tensions: Measurements at the Mainz vertical wind tunnel

Abstract Important characteristics of raindrops pertinent to fields in atmospheric sciences such as weather radar or pollution scavenging are drop shape, oscillation frequency and amplitude, as well as the internal circulation. Atmospheric raindrops are never pure water drops but contain additional components like aerosol particles and dissolved species. Surface active substances, when present, reduce the surface tension of raindrops and, thus, increase the drop deformation which in turn affects breakup and coalescence, pollutant scavenging, and, finally, the formation of precipitation. Experiments were performed at the Mainz vertical wind tunnel with raindrops freely suspended at their ter…

Aerosol concentrations determine the height of warm rain and ice initiation in convective clouds over the Amazon basin

Abstract. We have investigated how pollution aerosols affect the height above cloud base of rain and ice hydrometeor initiation and the subsequent vertical evolution of cloud droplet size and number concentrations in growing convective cumulus. For this purpose we used in-situ data of hydrometeor size distributions measured with instruments mounted on HALO (High Altitude and Long Range Research Aircraft) during the ACRIDICON-CHUVA campaign over the Amazon during September 2014. The results show that the height of rain initiation by collision and coalescence processes (Dr, in units of meters above cloud base) is linearly correlated with the number concentration of droplets (Nd in cm−3) nucle…

Characterization of a Modified Expansion Condensation Particle Counter for Detection of Nanometer-Sized Particles

A newly developed condensation particle counter provides measurements of aerosol particle number densities for size diameters as low as 3 nm. This Expansion Condensation Particle Counter (ECPC) operates based on fast adiabatic expansion with specialized detection and evaluation of the temporal development of light scattered by the ensemble of growing droplets. In its new configuration the ECPC has been modified such that a previously needed calibration factor became obsolete. In this article the new design is described which now includes a fast pressure sensor for monitoring the pressure drop inside the measurement chamber. Extensive laboratory experiments for characterizing the ECPC are de…

3-D imaging and quantification of graupel porosity by synchrotron-based micro-tomography

The air bubble structure is an important parameter to determine the radiation properties of graupel and hailstones. For 3-D imaging of this structure at micron resolution, a cryo-stage was developed. This stage was used at the tomography beamline of the Swiss Light Source (SLS) synchrotron facility. The cryo-stage setup provides for the first time 3-D-data on the individual pore morphology of ice particles down to infrared wavelength resolution. In the present study, both sub-mm size natural and artificial ice particles rimed in a wind tunnel were investigated. In the natural rimed ice particles, Y-shaped air-filled closed pores were found. When kept for half an hour at −8 °C, this morpholo…

Sub 500 nm refractory carbonaceous particles in the polar stratosphere

Abstract. Eleven particle samples collected in the polar stratosphere during SOLVE (SAGE III Ozone loss and validation experiment) from January until March 2000 were characterized in detail by high-resolution transmission and scanning electron microscopy (TEM/SEM) combined with energy-dispersive X-ray microanalysis. A total number of 4175 particles (TEM = 3845; SEM = 330) was analyzed from these samples which were collected mostly inside the polar vortex in the altitude range between 17.3 and 19.9 km. By particle volume, all samples are dominated by volatile particles (ammonium sulfates/hydrogen sulfates). By number, approximately 28–82 % of the particles are refractory carbonaceous with si…

NATO ARW on Clouds — Session Summaries

The two papers presented in this session focused on the role of dynamics in the water vapor distribution of the tropics and its implications to climate.

Detection of security relevant substances within the cooperative project SAFE XUV

The objective of this project funded by the German BMBF was to show that security relevant substances can be detected in complex matrices at low concentrations using single photon ionization ion trap mass spectrometry (SPI-ITMS). The advantage of such a soft ionization technique is a reduction of unwanted fragment ions in mass spectra allowing identification of signals from complex matrices and enabling MS/MS capability. The MS/MS studies permit low false-positive and false-negative rates. Additionally, the accumulation of the ions in the ion trap decreases the detection limit. To obtain low detection limits the ionization potentials (IPs) of the relevant substances have to be below the IPs…

In-Situ observation of New Particle Formation in the upper troposphere/lower stratosphere of the Asian Monsoon Anticyclone

Abstract. During the monsoon season of the year 2017 the airborne StratoClim mission took place in Kathmandu, Nepal with eight mission flights of the M-55 Geophysica in the upper troposphere/lower stratosphere (UT/LS) of the Asian Monsoon Anticyclone (AMA) over northern India, Nepal and Bangladesh. More than hundred events of New Particle Formation (NPF) were observed. In total, more than two hours of flight time were spent under NPF conditions as indicated by the abundant presence of ultrafine aerosols, i.e. with particle diameters dp smaller than 15 nm, which were in-situ detected by means of condensation nuclei counting techniques. Mixing ratios of ultrafine particles (nuf) of up to ~ 50…

New particle formation inside ice clouds: In-situ observations in the tropical tropopause layer of the 2017 Asian Monsoon Anticyclone

Abstract. From 27 July to 10 August 2017 the airborne StratoClim mission took place in Kathmandu, Nepal where eight mission flights were conducted with the M-55 Geophysica up to altitudes of 20 km. New Particle Formation (NPF) was identified by the abundant presence of ultrafine aerosols, with particle diameters dp smaller than 15 nm, which were in-situ detected by means of condensation nuclei counting techniques. NPF fields in clear-skies as well as in the presence of cloud ice particles (dp > 3 µm) were encountered at upper troposphere/lowermost stratosphere (UT/LS) levels and within the Asian Monsoon Anticyclone (AMA). NPF-generated ultrafine particles in elevated concentrations (Nuf)…

The impact of mineral dust on cloud formation during the Saharan dust event in April 2014 over Europe

A regional modeling study on the impact of desert dust on cloud formation is presented for a major Saharan dust outbreak over Europe from 2 to 5 April 2014. The dust event coincided with an extensive and dense cirrus cloud layer, suggesting an influence of dust on atmospheric ice nucleation. Using interactive simulation with the regional dust model COSMO-MUSCAT, we investigate cloud and precipitation representation in the model and test the sensitivity of cloud parameters to dust–cloud and dust–radiation interactions of the simulated dust plume. We evaluate model results with ground-based and spaceborne remote sensing measurements of aerosol and cloud properties, as well as the in situ meas…

ML-CIRRUS: The Airborne Experiment on Natural Cirrus and Contrail Cirrus with the High-Altitude Long-Range Research Aircraft HALO

Abstract The 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 combi…

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 Mount Okmok and Mount 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 between 27 October and 2 November 2008, the volcanic aerosol was measured by an Aerodyne aerosol mass spectrometer, capable of particle chemical composition measurements covering a size diameter range between 40 nm and 1 mm. In the volcanic aerosol layer enhanced submicron particulate sulfate concentrations of up to 2.0 mg m−3 standard temperature and pressure (STP) were observed between 8 and 12 km altitude, while background values …

Cross-hemispheric transport of central African biomass burning pollutants: implications for downwind ozone production

Pollutant plumes with enhanced concentrations of trace gases and aerosols were observed over the southern coast of West Africa during August 2006 as part of the AMMA wet season field campaign. Plumes were observed both in the mid and upper troposphere. In this study we examined the origin of these pollutant plumes, and their potential to photochemically produce ozone (O<sub>3</sub>) downwind over the Atlantic Ocean. Their possible contribution to the Atlantic O<sub>3</sub> maximum is also discussed. Runs using the BOLAM mesoscale model including biomass burning carbon monoxide (CO) tracers were used to confirm an origin from central African biomass burning fires. The…

Comparing calculated microphysical properties of tropical convective clouds at cloud base with measurements during the ACRIDICON-CHUVA campaign

Abstract. Reliable aircraft measurements of cloud microphysical properties are essential for understanding liquid convective cloud formation. In September 2014, the properties of convective clouds were measured with a Cloud Combination Probe (CCP), a Cloud and Aerosol Spectrometer (CAS-DPOL), and a cloud condensation nuclei (CCN) counter on board the HALO (High Altitude and Long Range Research Aircraft) aircraft during the ACRIDICON-CHUVA campaign over the Amazon region. An intercomparison of the cloud drop size distributions (DSDs) and the cloud water content derived from the different instruments generally shows good agreement within the instrumental uncertainties. The objective of this s…

Application of mobile aerosol and trace gas measurements for the investigation of megacity air pollution emissions: the Paris metropolitan area

For the investigation of megacity emission development and the impact outside the source region, mobile aerosol and trace gas measurements were carried out in the Paris metropolitan area between 1 July and 31 July 2009 (summer conditions) and 15 January and 15 February 2010 (winter conditions) in the framework of the European Union FP7 MEGAPOLI project. Two mobile laboratories, MoLa and MOSQUITA, were deployed, and here an overview of these measurements and an investigation of the applicability of such measurements for the analysis of megacity emissions are presented. Both laboratories measured physical and chemical properties of fine and ultrafine aerosol particles as well as gas phase con…

Effective broadband refractive index retrieval by a white light optical particle counter.

A new approach to retrieve the effective broadband refractive indices (nbroad,eff) of aerosol particles by a white light aerosol spectrometer (WELAS) optical particle counter (OPC) is presented. Using a tandem differential mobility analyzer (DMA)-OPC system, the nbroad,eff are obtained for both laboratory and field applications. This method was tested in the laboratory using substances with a wide range of optical properties. With the obtained nbroad,eff, WELAS aerosol size distributions can be corrected. Therefore, this method can be used for instrument calibration in both laboratory and field measurements. The retrieved effective broadband refractive indices for the scattering aerosols we…

Overview: On the transport and transformation of pollutants in the outflow of major population centres - Observational data from the EMeRGe European intensive operational period in summer 2017

Megacities and other major population centres (MPCs) worldwide are major sources of air pollution, both locally as well as downwind. The overall assessment and prediction of the impact of MPC pollution on tropospheric chemistry are challenging. The present work provides an overview of the highlights of a major new contribution to the understanding of this issue based on the data and analysis of the EMeRGe (Effect of Megacities on the transport and transformation of pollutants on the Regional to Global scales) international project. EMeRGe focuses on atmospheric chemistry, dynamics, and transport of local and regional pollution originating in MPCs. Airborne measurements, taking advantage of …

In-situ observations of young contrails – overview and selected results from the CONCERT campaign

Lineshaped contrails were detected with the research aircraft Falcon during the CONCERT – CONtrail and Cirrus ExpeRimenT – campaign in October/November 2008. The Falcon was equipped with a set of instruments to measure the particle size distribution, shape, extinction and chemical composition as well as trace gas mixing ratios of sulfur dioxide (SO<sub>2</sub>), reactive nitrogen and halogen species (NO, NO<sub>y</sub>, HNO<sub>3</sub>, HONO, HCl), ozone (O<sub>3</sub>) and carbon monoxide (CO). During 12 mission flights over Europe, numerous contrails, cirrus clouds and a volcanic aerosol layer were probed at altitudes between 8.5 and 11.6 km…

Complementary online aerosol mass spectrometry and offline FT-IR spectroscopy measurements: Prospects and challenges for the analysis of anthropogenic aerosol particle emissions

Abstract The aerosol mass spectrometer (AMS) is well established in investigating highly time-resolved dynamics of submicron aerosol chemical composition including organic aerosol (OA). However, interpretation of mass spectra on molecular level is limited due to strong fragmentation of organic substances and potential reactions inside the AMS ion chamber. Results from complementary filter-based FT-IR absorption measurements were used to explain features in high-resolution AMS mass spectra of different types of OA (e.g. cooking OA, cigarette smoking OA, wood burning OA). Using this approach some AMS fragment ions were validated in this study as appropriate and rather specific markers for a c…

Sensitivities of Amazonian clouds to aerosols and updraft speed

Abstract. The effects of aerosol particles and updraft speed on warm-phase cloud microphysical properties are studied in the Amazon region as part of the ACRIDICON-CHUVA experiment. Here we expand the sensitivity analysis usually found in the literature by concomitantly considering cloud evolution, putting the sensitivity quantifications into perspective in relation to in-cloud processing, and by considering the effects on droplet size distribution (DSD) shape. Our in situ aircraft measurements over the Amazon Basin cover a wide range of particle concentration and thermodynamic conditions, from the pristine regions over coastal and forested areas to the southern Amazon, which is highly poll…

In situ and lidar observations of tropopause subvisible cirrus clouds during TC4

[1] During the Tropical Composition, Clouds, and Climate Coupling (TC4) experiment in July–August 2007, the NASA WB-57F and ER-2 aircraft made coordinated flights through a tropopause subvisible cirrus (SVC) layer off the Pacific Coast of Central America. The ER-2 aircraft was equipped with a remote sensing payload that included the cloud physics lidar (CPL). The WB-57F payload included cloud microphysical and trace gas measurements, and the aircraft made four vertical profiles through the SVC layer shortly after the ER-2 flew over. The in situ and remotely sensed data are used to quantify the meteorological and microphysical properties of the SVC layer, and these data are compared to the l…

Chemical composition of ambient aerosol, ice residues and cloud droplet residues in mixed-phase clouds: single particle analysis during the Cloud and Aerosol Characterization Experiment (CLACE 6)

Abstract. Two different single particle mass spectrometers were operated in parallel at the Swiss High Alpine Research Station Jungfraujoch (JFJ, 3580 m a.s.l.) during the Cloud and Aerosol Characterization Experiment (CLACE 6) in February and March 2007. During mixed phase cloud events ice crystals from 5–20 μm were separated from larger ice aggregates, non-activated, interstitial aerosol particles and supercooled droplets using an Ice-Counterflow Virtual Impactor (Ice-CVI). During one cloud period supercooled droplets were additionally sampled and analyzed by changing the Ice-CVI setup. The small ice particles and droplets were evaporated by injection into dry air inside the Ice-CVI. The …

How villages contribute to their local air quality – The influence of traffic- and biomass combustion-related emissions assessed by mobile mappings of PM and its components

Abstract Mobile mapping experiments were performed in two villages (~400 and ~2500 inhabitants, respectively) in France and Germany in both summer and winter in order to assess the pollutant distribution of several particulate matter (PM) related pollutants (particle number concentration, PM1, PM2.5, PM10; PM1 chemical composition, including inorganic and organic species, black carbon, and polyaromatic hydrocarbons) as well as CO2. Two dominating local emission contributions were found: traffic contributed to organic aerosol (OA), CO2, particle number concentration, PM1, black carbon, and polyaromatic hydrocarbons, whereas significant primary emission contributions from biomass combustion w…

In-line holography of cloud volumes applied to the measurement of raindrops and snowflakes

Abstract The ground-based HODAR (HOlographic Droplet and Aerosol Recording) of the University of Mainz has been operational since 1989 on the Kleiner Feldberg Mountain Observatory near Frankfurt/Main, Germany, in a `small volume' configuration. With this setup an air volume of approximately 1 l can be in situ recorded, which allows it to image all aerosol particles and droplets with diameter larger than 6 μm contained in the sample volume in situ. Recently the beam diameter and optical path length of the inline system have been enlarged such that large cloud volumes (approximately 500 l) can be recorded on single holograms. During the holographic image reconstruction step in the laboratory,…

Holographic in-situ measurements of the spatial droplet distribution in stratiform clouds

Ground based in-situ measurements on the small-scale structure of low-level stratiform clouds have been performed utilizing the HOlographic Droplet and Aerosol Recording system (HODAR) of the University of Mainz, Germany. 6 holograms recorded during stratus cloud events on the Kleiner Feldberg Taunus Mountain Observatory (Frankfurt, Germany) were reconstructed in the laboratory and analysed by means of an automated data extraction and image processing system. In post-processing, each originally recorded droplet population was subjected to 2 statistical methods: (1) the sub-cell scanning analyses with statistical “Fishing” tests and (2) measurements of inter-droplet distance frequency distri…

Comparing parameterized versus measured microphysical properties of tropical convective cloud bases during the ACRIDICON–CHUVA campaign

The objective of this study is to validate parameterizations that were recently developed for satellite retrievals of cloud condensation nuclei supersaturation spectra, NCCN(S), at cloud base alongside more traditional parameterizations connecting NCCN(S) with cloud base updrafts and drop concentrations. This was based on the HALO aircraft measurements during the ACRIDICON–CHUVA campaign over the Amazon region, which took place in September 2014. The properties of convective clouds were measured with a cloud combination probe (CCP), a cloud and aerosol spectrometer (CAS-DPOL), and a CCN counter onboard the HALO aircraft. An intercomparison of the cloud drop size distributions (DSDs) and the…

Spectral optical layer properties of cirrus from collocated airborne measurements – a feasibility study

Abstract. Spectral optical layer properties of cirrus are derived from simultaneous and vertically collocated measurements of spectral upward and downward solar irradiance above and below the cloud layer and concurrent in situ microphysical sampling. From the irradiance data spectral transmissivity, absorptivity, reflectivity, and cloud top albedo of the observed cirrus layer are obtained. At the same time microphysical properties of the cirrus were sampled. The close collocation of the radiative and microphysical measurements, above, beneath and inside the cirrus, is obtained by using a research aircraft (Learjet 35A) in tandem with a towed platform called AIRTOSS (AIRcraft TOwed Sensor Sh…

Aircraft-based observation of meteoric material in lower-stratospheric aerosol particles between 15 and 68° N

We analyse aerosol particle composition measurements from five research missions between 2014 and 2018 to assess the meridional extent of particles containing meteoric material in the upper troposphere and lower stratosphere (UTLS). Measurements from the Jungfraujoch mountaintop site and a low-altitude aircraft mission show that meteoric material is also present within middle- and lower-tropospheric aerosol but within only a very small proportion of particles. For both the UTLS campaigns and the lower- and mid-troposphere observations, the measurements were conducted with single-particle laser ablation mass spectrometers with bipolar-ion detection, which enabled us to measure the chemical c…

The potential of cirrus clouds for heterogeneous chlorine activation

The ER-2 data from ascents and descents through layers of cirrus clouds are utilized to study the heterogeneous reactions of ClONO 2 with H 2 O, of HOCl and ClONO 2 with HCl, and their potential role for the activation of chlorine in the tropopause regions which could affect ozone there. Lacking measured data for the three chlorine containing molecules their abundances as a function of altitude have been calculated from a 2D model. The aerosol surface data measured by a Forward Scattering Spectrometer Probe (FSSP-300) on the ER-2 were corrected for the expected asphericity of cirrus cloud particles by means of a T-matrix method. The results indicate considerable potential of cirrus clouds f…

Ultrathin Tropical Tropopause Clouds (UTTCs) : I. Cloud morphology and occurrence

Abstract. Subvisible cirrus clouds (SVCs) may contribute to dehydration close to the tropical tropopause. The higher and colder SVCs and the larger their ice crystals, the more likely they represent the last efficient point of contact of the gas phase with the ice phase and, hence, the last dehydrating step, before the air enters the stratosphere. The first simultaneous in situ and remote sensing measurements of SVCs were taken during the APE-THESEO campaign in the western Indian ocean in February/March 1999. The observed clouds, termed Ultrathin Tropical Tropopause Clouds (UTTCs), belong to the geometrically and optically thinnest large-scale clouds in the Earth's atmosphere. Individual UT…

Particulate trimethylamine in the summertime Canadian high Arctic lower troposphere

Abstract. Size-resolved and vertical profile measurements of single particle chemical composition (sampling altitude range 50–3000 m) were conducted in July 2014 in the Canadian high Arctic during the aircraft-based measurement campaign NETCARE 2014. We deployed the single particle laser ablation aerosol mass spectrometer ALABAMA (vacuum aerodynamic diameter range approximately 200–1000 nm) to identify different particle types and their mixing states. On basis of the single particle analysis, we found that a significant fraction (23 %) of all analyzed particles (in total: 7412) contained trimethylamine (TMA). The identification of TMA in ambient mass spectra was confirmed by laboratory meas…

Mixed-Phase Clouds: Progress and Challenges

Mixed-phase clouds represent a three-phase colloidal system consisting of water vapor, ice particles, and coexisting supercooled liquid droplets. Mixed-phase clouds are ubiquitous in the troposphere, occurring at all latitudes from the polar regions to the tropics. Because of their widespread nature, mixed-phase processes play critical roles in the life cycle of clouds, precipitation formation, cloud electrification, and the radiative energy balance on both regional and global scales. Yet, in spite of many decades of observations and theoretical studies, our knowledge and understanding of mixed-phase cloud processes remains incomplete. Mixed-phase clouds are notoriously difficult to represe…

The ion trap aerosol mass spectrometer: improved design, first field deployment, and the capability of differentiating organic compound classes via MS–MS

Abstract. Further development and optimisation of a previously described ion trap aerosol mass spectrometer (IT-AMS) are presented, which resulted in more reproducible and robust operation and allowed for the instrument’s first field deployment. Results from this 11-day long measurement indicate that the instrument is capable of providing quantitative information on organics, nitrate, and sulphate mass concentrations with reasonable detection limits (0.5–1.4 µg m−3 for 1 h averages), and that results obtained with the IT-AMS can directly be related to those from Aerodyne aerosol mass spectrometers. The capability of the IT-AMS to elucidate the structure of fragment ions is demonstrated via …

The ATAL within the 2017 Asian Monsoon Anticyclone: Microphysical aerosol properties derived from aircraft-borne in situ measurements

Abstract. The Asian summer monsoon is an effective pathway for aerosol particles and precursor substances from the planetary boundary layer over Central, South, and East Asia into the upper troposphere and lower stratosphere. An enhancement of aerosol particles within the Asian monsoon anticyclone (AMA) has been observed by satellites, called the Asian Tropopause Aerosol Layer (ATAL). In this paper we discuss airborne in situ and remote sensing observations of aerosol microphysical properties conducted during the 2017 StratoClim field campaign within the region of the Asian monsoon anticyclone. The aerosol particle measurements aboard the high-altitude research aircraft M55 Geophysica (reac…

Observations of meteoric material and implications for aerosol nucleation in the winter Arctic lower stratosphere derived from in situ particle measurements

Number concentrations of total and non-volatile aerosol particles with size diameters >0.01 μm as well as particle size distributions (0.4–23 μm diameter) were measured in situ in the Arctic lower stratosphere (10–20.5 km altitude). The measurements were obtained during the campaigns European Polar Stratospheric Cloud and Lee Wave Experiment (EUPLEX) and Envisat-Arctic-Validation (EAV). The campaigns were based in Kiruna, Sweden, and took place from January to March 2003. Measurements were conducted onboard the Russian high-altitude research aircraft Geophysica using the low-pressure Condensation Nucleus Counter COPAS (COndensation PArticle Counter System) and a modified F…

Mass-spectrometric identification of primary biological particle markers: indication for low abundance of primary biological material in the pristine submicron aerosol of Amazonia

Abstract. The abundance of marker compounds for primary biological particles in submicron aerosol was investigated by means of aerosol mass spectrometry. Mass spectra of amino acids, carbohydrates, small peptides, and proteins, all of which are key building blocks of biological particles, were recorded in laboratory experiments. Several characteristic marker peaks were identified. The identified marker peaks were compared with mass spectra recorded during AMAZE-08, a field campaign conducted in the pristine rainforest of the Central Amazon Basin, Brazil, during the wet season of February and March 2008. The low abundance of identified marker peaks places upper limits of 7.5 % for amino acid…

Characterization of a Newly Developed Aircraft-Based Laser Ablation Aerosol Mass Spectrometer (ALABAMA) and First Field Deployment in Urban Pollution Plumes over Paris During MEGAPOLI 2009

We present here the development and first field deployment of a novel Aircraft-based Laser ABlation Aerosol MAss spectrometer (ALABAMA), which is capable of measuring the chemical composition and size of individual ambient aerosol particles in the size range between 150 and 900 nm. The instrument uses a continuous wave 532 nm laser to size and detect the particles, a pulsed 266 nm laser to ablate and ionize the particles, and a bipolar, Z-shaped time-of-flight mass spectrometer to detect positive and negative ions. The ALABAMA fits into a 19"-aircraft rack of 150 cm height and has a total weight of 140 kg, thus currently being one of the smallest and lightest-weight instruments of its type.…

In situ, satellite measurement and model evidence on the dominant regional contribution to fine particulate matter levels in the Paris megacity

International audience; Published by Copernicus Publications on behalf of the European Geosciences Union. 9578 M. Beekmann et al.: Evidence for a dominant regional contribution to fine particulate matter levels Abstract. A detailed characterization of air quality in the megacity of Paris (France) during two 1-month intensive campaigns and from additional 1-year observations revealed that about 70 % of the urban background fine particulate matter (PM) is transported on average into the megacity from upwind regions. This dominant influence of regional sources was confirmed by in situ measurements during short intensive and longer-term campaigns, aerosol optical depth (AOD) measurements from E…

Chemical analysis of the Asian tropopause aerosol layer (ATAL) with emphasis on secondary aerosol particles using aircraft-based in situ aerosol mass spectrometry

Abstract. Aircraft-borne in situ measurements of the chemical aerosol composition were conducted in the Asian tropopause aerosol layer (ATAL) over the Indian subcontinent in the summer of 2017, covering particle sizes below ∼3 µm. We have implemented a recently developed aerosol mass spectrometer, which adopts the laser desorption technique as well as the thermal desorption method for quantitative bulk information (i.e., a modified Aerodyne AMS), aboard the high-altitude research aircraft M-55 Geophysica. The instrument was deployed in July and August 2017 during the StratoClim EU campaign (Stratospheric and upper tropospheric processes for better Climate predictions) over Nepal, India, Ban…

Enhanced organic mass fraction and decreased hygroscopicity of cloud condensation nuclei (CCN) during new particle formation events

In a forested near-urban location in central Germany, the CCN efficiency of particles smaller than 100 nm decreases significantly during periods of new particle formation. This results in an increase of average activation diameters, ranging from 5 to 8% at supersaturations of 0.33% and 0.74%, respectively. At the same time, the organic mass fraction in the sub-100-nm size range increases from approximately 2/3 to 3/4. This provides evidence that secondary organic aerosol (SOA) components are involved in the growth of new particles to larger sizes, and that the reduced CCN efficiency of small particles is caused by the low hygroscopicity of the condensing material. The observed dependence of…

Measurements of aerosol and CCN properties in the Mackenzie River delta (Canadian Arctic) during spring–summer transition in May 2014

Within the framework of the RACEPAC (Radiation–Aerosol–Cloud Experiment in the Arctic Circle) project, the Arctic aerosol, arriving at a ground-based station in Tuktoyaktuk (Mackenzie River delta area, Canada), was characterized during a period of 3 weeks in May 2014. Basic meteorological parameters and particle number size distributions (PNSDs) were observed and two distinct types of air masses were found. One type were typical Arctic haze air masses, termed accumulation-type air masses, characterized by a monomodal PNSD with a pronounced accumulation mode at sizes above 100 nm. These air masses were observed during a period when back trajectories indicate an air mass origin in the north-e…

Optimizing the detection, ablation, and ion extraction efficiency of a single-particle laser ablation mass spectrometer for application in environments with low aerosol particle concentrations

The aim of this study is to show how a newly developed aerodynamic lens system (ALS), a delayed ion extraction (DIE), and better electric shielding improve the efficiency of the Aircraft-based Laser ABlation Aerosol MAss spectrometer (ALABAMA). These improvements are applicable to single-particle laser ablation mass spectrometers in general. To characterize the modifications, extensive size-resolved measurements with spherical polystyrene latex particles (PSL; 150–6000 nm) and cubic sodium chloride particles (NaCl; 400–1700 nm) were performed. Measurements at a fixed ALS position show an improved detectable particle size range of the new ALS compared to the previously used Liu…

Contribution of the gas-phase reaction between hydroxyl radical and sulfur dioxide to the sulfate aerosol over West Pacific

Sulfate is among the major components of atmospheric aerosols or fine particulate matters. Aerosols loaded with sulfate result in low air quality, damage to ecosystems, and influences on climate change. Sulfate aerosols could originate from that directly emitted to the atmosphere and that produced by atmospheric physicochemical processes. The latter is generated from sulfur dioxide (SO2) via oxidation either in the gas phase reactions or in the aqueous phase. Several mechanisms of SO2 oxidation have been proposed, but the differentiation of the various mechanisms and identification of the sources remain challenging. To meet this need, a new method to estimate the contribution of the gas-pha…

Dehydration potential of ultrathin clouds at the tropical tropopause

[1] We report on the first simultaneous in situ and remote measurements of subvisible cirrus in the uppermost tropical troposphere. The observed cirrus, called UTTCs ( ultrathin tropical tropopause clouds), are the geometrically (200-300 m) and optically (t approximate to 10(-4)) thinnest large-scale clouds ever sampled (approximate to10(5) km(2)). UTTCs consist of only a few ice particles per liter with mean radius approximate to5 mum, containing only 1-5 % of the total water. Yet, brief adiabatic cooling events only 1-2 K below mean ambient temperature destabilize UTTCs, leading to large sedimenting particles (r approximate to 25 mm). Due to their extreme altitude above 17 km and low part…

Instrument intercomparison study on cloud droplet size distribution measurements: Holography vs. laser optical particle counter

During the EUROTRAC Ground Based Cloud Experiment (GCE) 1990, a newly developed HODAR (Holographic Droplet and Aerosol Recording) was operated for the first time to measure cloud droplet size distributions by recording Fraunhofer in-line holograms of small cloud sample volumes in situ and analyzing the holographic images in the laboratory.

Nucleation particles in diesel exhaust: composition inferred from in situ mass spectrometric analysis.

Mass spectrometric measurements of size and composition of diesel exhaust particles have been performed under various conditions: chassis dynamometer tests, field measurements near a German motorway, and individual car chasing. Nucleation particles consisting of volatile sulfate and organic material could be detected both at the chassis dynamometer test facility and during individual car chasing. We found evidence that if nucleation occurs, sulfuric acid/water is the nucleating agent. Low-volatile organics species condense only on the preexisting sulfuric acid/water clusters. Nucleation was found to depend strongly on various parameters such as exhaust dilution conditions, fuel sulfur conte…

Stratospheric Aerosols After Pinatubo: Results from the 1991/2 Airborne Arctic Stratospheric Expedition (AASE II)

The Airborne Arctic Stratospheric Expedition II involved measurements of key quantities concerning the chemistry and physics of the stratospheric ozone loss from the NASA operated DC-8 and ER-2 platforms. The series of AASE II flights was conducted between August 22, 1991, until March 26, 1992, from Moffett Field (California), Fairbanks (Alaska), and Bangor (Maine). The timing and location of the AASE II flights permitted to obtain a large data basis pertaining to the effects of the Mt. Pinatubo volcanic plume spreading in the northern hemispheric stratosphere. This contribution presents results obtained from the ER-2 in-situ measurements up to altitudes of ≈ 20 km in the polar stratosphere…

In-Situ Measurements of the Cloud Microphysical Structure Using Holography

Arctic low-level boundary layer clouds: in situ measurements and simulations of mono- and bimodal supercooled droplet size distributions at the top layer of liquid phase clouds

Abstract. Aircraft borne optical in situ size distribution measurements were performed within Arctic boundary layer clouds with a special emphasis on the cloud top layer during the VERtical Distribution of Ice in Arctic clouds (VERDI) campaign in April and May 2012. An instrumented Basler BT-67 research aircraft operated out of Inuvik over the Mackenzie River delta and the Beaufort Sea in the Northwest Territories of Canada. Besides the cloud particle and hydrometeor size spectrometers the aircraft was equipped with instrumentation for aerosol, radiation and other parameters. Inside the cloud, droplet size distributions with monomodal shapes were observed for predominantly liquid-phase Arct…

Nitric Acid Trihydrate (NAT) formation at low NAT supersaturation in Polar Stratospheric Clouds (PSCs)

International audience; A PSC was detected on 6 February 2003 in the Arctic stratosphere by in-situ measurements onboard the high-altitude research aircraft Geophysica. Low number densities (~10-4cm-3) of small nitric acid (HNO3) containing particles (dTNAT, these NAT particles have the potential to grow further and to remove HNO3 from the stratosphere, thereby enhancing polar ozone loss. Interestingly, the NAT particles formed in less than a day at temperatures just slightly below TNAT (T>TNAT-3.1K). This unique measurement of PSC formation at extremely low NAT saturation ratios (SNAT?10) constrains current NAT nucleation theories. We suggest, that the NAT particles have formed heterogeneo…

Long-lived contrails and convective cirrus above the tropical tropopause

Abstract. This study has two objectives: (1) it characterizes contrails at very low temperatures and (2) it discusses convective cirrus in which the contrails occurred. (1) Long-lived contrails and cirrus from overshooting convection are investigated above the tropical tropopause at low temperatures down to −88 °C from measurements with the Russian high-altitude research aircraft M-55 Geophysica, as well as related observations during the SCOUT-O3 field experiment near Darwin, Australia, in 2005. A contrail was observed to persist below ice saturation at low temperatures and low turbulence in the stratosphere for nearly 1 h. The contrail occurred downwind of the decaying convective system H…

Chemical analysis of the Asian Tropopause Aerosol Layer (ATAL) with emphasis on secondary aerosol particles using aircraft based in situ aerosol mass spectrometry

Abstract. Aircraft borne in-situ measurements of the chemical aerosol composition were conducted in the Asian Tropopause Aerosol layer (ATAL) over the Indian subcontinent in summer 2017 covering particle sizes below 3 µm. We have implemented a recently developed aerosol mass spectrometer, which adopts the laser desorption technique as well as the thermal desorption method for quantitative bulk information (i.e. a modified Aerodyne AMS), aboard the high altitude research aircraft M-55 Geophysica. The instrument was deployed in July and August 2017 during the StratoClim EU campaign (Stratospheric and upper tropospheric processes for better climate predictions) over Nepal, India, Bangladesh, a…

Performance of a Focused Cavity Aerosol Spectrometer for Measurements in the Stratosphere of Particle Size in the 0.06–2.0-µm-Diameter Range

A focused cavity aerosol spectrometer aboard a NASA ER-2 high-altitude aircraft provided high-resolution measurements of the size of the stratospheric particles in the 0.06-2.0-micrometer-diameter range in flights following the eruption of Mount Pinatubo in 1991. Effects of anisokinetic sampling and evaporation in the sampling system were accounted for by means adapted and specifically developed for this instrument. Calibrations with monodisperse aerosol particles provided the instrument's response matrix, which upon inversion during data reduction yielded the particle size distributions. The resultant dataset is internally consistent and generally shows agreement to within a factor of 2 wi…

The Kleiner Feldberg Cloud Experiment 1990. An overview

An overview is given of the Kleiner Feldberg cloud experiment performed from 27 October until 13 November 1990. The experiment was carried out by numerous European research groups as a joint effort within the EUROTRAC-GCE project in order to study the interaction of cloud droplets with atmospheric trace constituents. After a description of the observational site and the measurements which were performed, the general cloud formation mechanisms encountered during the experiment are discussed. Special attention is given here to the process of moist adiabatic lifting. Furthermore, an overview is given regarding the pollutant levels in the gas phase, the particulate and the liquid phase, and som…

In situ measurements of background aerosol and subvisible cirrus in the tropical tropopause region

[1] In situ aerosol measurements were performed in the Indian Ocean Intertropical Convergence Zone (ITCZ) region during the Airborne Polar Experiment-Third European Stratospheric Experiment on Ozone (APE-THESEO) field campaign based in Mahe, Seychelles between 24 February and 6 March 1999. These are measurements of particle size distributions with a laser optical particle counter of the Forward Scattering Spectrometer Probe (FSSP)-300 type operated on the Russian M-55 high-altitude research aircraft Geophysica in the tropical upper troposphere and lower stratosphere up to altitudes of 21 km. On 24 and 27 February 1999, ultrathin layers of cirrus clouds were penetrated by Geophysica directly…

Variability of aerosol, gaseous pollutants and meteorological characteristics associated with continental, urban and marine air masses at the SW Atlantic coast of Iberia

Abstract. Measurements of the ambient aerosol were performed at the Southern coast of Spain, within the framework of the DOMINO (Diel Oxidant Mechanisms In relation to Nitrogen Oxides) project. The field campaign took place from 20 November until 9 December 2008 at the atmospheric research station "El Arenosillo" (37°5'47.76" N, 6&deg44'6.94" W). As the monitoring station is located at the interface between a natural park, industrial cities (Huelva, Seville) and the Atlantic Ocean a variety of physical and chemical parameters of aerosols and gas phase could be characterized in dependency on the origin of air masses. Backwards trajectories were examined and compared with local meteor…

Application of an O-ring pinch device as a constant pressure inlet (CPI) for airborne sampling

Abstract. We present a novel and compact design of a constant pressure inlet (CPI) developed for use in airborne aerosol mass spectrometry. In particular the inlet system is optimized for aerodynamic lenses commonly used in aerosol mass spectrometers, where efficient focusing of aerosol particles into a vacuum chamber requires a precisely controlled lens pressure, typically of a few hPa. The CPI device can also be used in gas phase sampling instruments in a large range of altitude and inlet pressure. The constant pressure is achieved by changing the inner diameter of a properly scaled O-ring that acts as a critical orifice. The CPI control keeps air pressure and thereby mass flow rate (≈ 0.…

The Effect of Turbulence on the Accretional Growth of Graupel

Abstract Wind tunnel experiments were carried out to investigate the influence of turbulence on the collection kernel of graupel. The collection kernel defines the growth rate of a graupel accreting supercooled droplets as it falls through a cloud. The ambient conditions were similar to those occurring typically in the mixed-phase zone of convective clouds, that is, at temperatures between −7° and −16°C and with liquid water contents from 0.5 to 1.3 g m−3. Tethered spherical collectors with radii between 220 and 340 μm were exposed in a flow carrying supercooled droplets with a mean volume radius of 10 μm. The vertical root-mean-square fluctuation velocity, the dissipation rate, and the Tay…

A tandem approach for collocated in-situ measurements of microphysical and radiative cirrus properties

Abstract. Microphysical and radiation measurements were collected with the unique AIRcraft TOwed Sensor Shuttle (AIRTOSS) – Learjet tandem platform. It is a combination of a Learjet 35A research aircraft and an instrumented aerodynamic body, which can be detached from and retracted back to the aircraft during flight. Both platforms are equipped with radiative, cloud microphysical, trace gas (CO, N2O, O3 and H2O) and meteorological instruments to study the inhomogeneity of cirrus as well as other layer clouds. Sophisticated numerical flow simulations were conducted in advance in order to optimally integrate a Cloud Combination Probe (CCP) inside the AIRTOSS. The tandem platform was used for …

The Asian tropopause aerosol layer within the 2017 monsoon anticyclone: microphysical properties derived from aircraft-borne in situ measurements

The Asian summer monsoon is an effective pathway for aerosol particles and precursors from the planetary boundary layer over Central, South, and East Asia into the upper troposphere and lower stratosphere. An enhancement of aerosol particles within the Asian monsoon anticyclone (AMA), called the Asian tropopause aerosol layer (ATAL), has been observed by satellites. We discuss airborne in situ and remote sensing observations of aerosol microphysical properties conducted during the 2017 StratoClim field campaign within the AMA region. The aerosol particle measurements aboard the high-altitude research aircraft M55 Geophysica (maximum altitude reached of ∼20.5 km) were conducted with a modifi…

Comparative study on immersion freezing utilizing single-droplet levitation methods

Immersion freezing experiments were performed utilizing two distinct single-droplet levitation methods. In the Mainz vertical wind tunnel, supercooled droplets of 700 µm diameter were freely floated in a vertical airstream at constant temperatures ranging from −5 to −30 ∘C, where heterogeneous freezing takes place. These investigations under isothermal conditions allow the application of the stochastic approach to analyze and interpret the results in terms of the freezing or nucleation rate. In the Mainz acoustic levitator, 2 mm diameter drops were levitated while their temperature was continuously cooling from +20 to −28 ∘C by adapting to the ambient temperature. Therefore, in this case th…

Enhanced Role of Transition Metal Ion Catalysis During In-Cloud Oxidation of SO2

Global sulfate production plays a key role in aerosol radiative forcing; more than half of this production occurs in clouds. We found that sulfur dioxide oxidation catalyzed by natural transition metal ions is the dominant in-cloud oxidation pathway. The pathway was observed to occur primarily on coarse mineral dust, so the sulfate produced will have a short lifetime and little direct or indirect climatic effect. Taking this into account will lead to large changes in estimates of the magnitude and spatial distribution of aerosol forcing. Therefore, this oxidation pathway-which is currently included in only one of the 12 major global climate models-will have a significant impact on assessmen…

Unprecedented evidence for deep convection hydrating the tropical stratosphere

[1] We report on in situ and remote sensing measurements of ice particles in the tropical stratosphere found during the Geophysica campaigns TROCCINOX and SCOUT-O3. We show that the deep convective systems penetrated the stratosphere and deposited ice particles at altitudes reaching 420 K potential temperature. These convective events had a hydrating effect on the lower tropical stratosphere due to evaporation of the ice particles. In contrast, there were no signs of convectively induced dehydration in the stratosphere.

Aircraft-based observation of meteoric material in lower stratospheric aerosol particles between 15 and 68° N

Abstract. In this paper we analyze aerosol particle composition measurements from five research missions conducted between 2014 and 2018 sampling the upper troposphere and lower stratosphere (UTLS), to assess the meridional extent of particles containing meteoric material. Additional data sets from a ground based study and from a low altitude aircraft mission are used to confirm the existence of meteoric material in lower tropospheric particles. Single particle laser ablation techniques with bipolar ion detection were used to measure the chemical composition of particles in a size range of approximately 150 nm to 3 μm. The five UTLS aircraft missions cover a latitude range from 15 to 68° N,…

A tandem approach for collocated measurements of microphysical and radiative cirrus properties

Microphysical and radiation measurements were collected with the novel AIRcraft TOwed Sensor Shuttle (AIRTOSS) – Learjet tandem platform. The platform is a combination of an instrumented Learjet 35A research aircraft and an aerodynamic bird, which is detached from and retracted back to the aircraft during flight via a steel wire with a length of 4000 m. Both platforms are equipped with radiative, cloud microphysical, trace gas, and meteorological instruments. The purpose of the development of this tandem set-up is to study the inhomogeneity of cirrus as well as other stratiform clouds. Sophisticated numerical flow simulations were conducted in order to optimally integrate an axially asymmet…

Further evidence for CCN aerosol concentrations determining the height of warm rain and ice initiation in convective clouds over the Amazon basin

We have investigated how aerosols affect the height above cloud base of rain and ice hydrometeor initiation and the subsequent vertical evolution of cloud droplet size and number concentrations in growing convective cumulus. For this purpose we used in situ data of hydrometeor size distributions measured with instruments mounted on HALO aircraft during the ACRIDICON–CHUVA campaign over the Amazon during September 2014. The results show that the height of rain initiation by collision and coalescence processes (Dr, in units of meters above cloud base) is linearly correlated with the number concentration of droplets (Nd in cm−3) nucleated at cloud base (Dr ≈ 5 ⋅ Nd). Additional cloud processes…

Design, characterization, and first field deployment of a novel aircraft-based aerosol mass spectrometer combining the laser ablation and flash vaporization techniques

In this paper, we present the design, development, and characteristics of the novel aerosol mass spectrometer ERICA (ERC Instrument for Chemical composition of Aerosols; ERC – European Research Council) and selected results from the first airborne field deployment. The instrument combines two well-established methods of real-time in situ measurements of fine particle chemical composition. The first method is the laser desorption and ionization technique, or laser ablation technique, for single-particle mass spectrometry (here with a frequency-quadrupled Nd:YAG laser at λ = 266 nm). The second method is a combination of thermal particle desorption, also called flash vaporization, and electro…

Impact of deep convection in the tropical tropopause layer in West Africa: in-situ observations and mesoscale modelling

Abstract. We present the analysis of the impact of convection on the composition of the tropical tropopause layer region (TTL) in West-Africa during the AMMA-SCOUT campaign. Geophysica M55 aircraft observations of water vapor, ozone, aerosol and CO2 during August 2006 show perturbed values at altitudes ranging from 14 km to 17 km (above the main convective outflow) and satellite data indicates that air detrainment is likely to have originated from convective cloud east of the flights. Simulations of the BOLAM mesoscale model, nudged with infrared radiance temperatures, are used to estimate the convective impact in the upper troposphere and to assess the fraction of air processed by convecti…

Holographic Observations of Centimeter-Scale Nonuniformities within Marine Stratocumulus Clouds

Abstract Data collected with a holographic instrument [Holographic Detector for Clouds (HOLODEC)] on board the High-Performance Instrumented Airborne Platform for Environmental Research Gulfstream-V (HIAPER GV) aircraft from marine stratocumulus clouds during the Cloud System Evolution in the Trades (CSET) field project are examined for spatial uniformity. During one flight leg at 1190 m altitude, 1816 consecutive holograms were taken, which were approximately 40 m apart with individual hologram dimensions of 1.16 cm × 0.68 cm × 12.0 cm and with droplet concentrations of up to 500 cm−3. Unlike earlier studies, minimally intrusive data processing (e.g., bypassing calculation of number concen…

Chemical composition and source attribution of sub-micrometre aerosol particles in the summertime Arctic lower troposphere

Aerosol particles impact the Arctic climate system both directly and indirectly by modifying cloud properties, yet our understanding of their vertical distribution, chemical composition, mixing state, and sources in the summertime Arctic is incomplete. In situ vertical observations of particle properties in the high Arctic combined with modelling analysis on source attribution are in short supply, particularly during summer. We thus use airborne measurements of aerosol particle composition to demonstrate the strong contrast between particle sources and composition within and above the summertime Arctic boundary layer. In situ measurements from two complementary aerosol mass spectrometers, t…

Stratospheric aerosol measurements in the Arctic winter of 1996/1997 with the M-55 Geophysika high-altitude research aircraft

In-situ aerosol measurements were performed in the northern hemispheric stratosphere up to altitudes of 21 km between 13 November 1996 and 14 January 1997, inside and outside of the polar vortex during the Airborne Polar Experiment (APE) field campaign. These are measurements of particle size distributions with a laser optical particle counter of the FSSP-300 type operated during 9 flights on the Russian M-55 high-altitude research aircraft Geophysika. For specific flights, the FSSP-300 measurements are compared with balloon-borne data (launched from Kiruna, Sweden). It was found that the stratospheric aerosol content reached levels well below the background concentrations measured by the N…

Aircraft-based operation of an aerosol mass spectrometer: Measurements of tropospheric aerosol composition

The Aerodyne quadrupole aerosol mass spectrometer was deployed on the Falcon twin jet research aircraft operated by Deutsches Zentrum für Luft- und Raumfahrt (DLR). This was the first deployment of an AMS in a jet aircraft. Aerosol mass concentration measurements in the troposphere up to altitudes of about 11 km were performed within two measurement flights on 12 and 14 May 2003 over southern Germany. Background aerosol data were gained up to 6 km, while aircraft exhaust aerosol was be sampled at higher altitudes on 14 May, indicating the presence of sulfuric acid and unburned hydrocarbons in the exhaust particles. The boundary layer aerosol on 12 May was found to be composed of 49% organic…

Ice supersaturations and cirrus cloud crystal numbers

Upper tropospheric observations outside and inside of cirrus clouds indicate water vapour mixing ratios sometimes exceeding water saturation. Relative humidities over ice (RHice) of up to and more than 200% have been reported from aircraft and balloon measurements in recent years. From these observations a lively discussion continues on whether there is a lack of understanding of ice cloud microphysics or whether the water measurements are tainted with large uncertainties or flaws. Here, RHice in clear air and in ice clouds is investigated. Strict quality-checked aircraft in situ observations of RHice were performed during 28 flights in tropical, mid-latitude and Arctic field experiments in…

In-situ observations and modeling of small nitric acid-containing ice crystals

Measurements in nascent ice forming regions are very rare and help understand cirrus cloud formation and the interactions of trace gases with ice crystals. A tenuous cirrus cloud has been probed with in-situ and remote sensing instruments onboard the high altitude research aircraft Geophysica M55 in the tropical upper troposphere. Besides microphysical and optical particle properties, water (H<sub>2</sub>O) and reactive nitrogen species (NO<sub>y</sub>) have been measured. In slightly ice supersaturated air between 14.2 and 14.9 km altitude, an unusually low ice water content of 0.031 mg m<sup>−3</sup> and small ice crystals with mean radii of 5…

Particle surface area dependence of mineral dust in immersion freezing mode: investigations with freely suspended drops in an acoustic levitator and a vertical wind tunnel

Abstract. The heterogeneous freezing temperatures of supercooled drops were measured using an acoustic levitator. This technique allows one to freely suspend single drops in the air without any wall contact. Heterogeneous nucleation by two types of illite (illite IMt1 and illite NX) and a montmorillonite sample was investigated in the immersion mode. Drops of 1 mm in radius were monitored by a video camera while cooled down to −28 °C to simulate freezing within the tropospheric temperature range. The surface temperature of the drops was contact-free, determined with an infrared thermometer; the onset of freezing was indicated by a sudden increase of the drop surface temperature. For compari…

A wind tunnel study of the effects of collision processes on the shape and oscillation for moderate-size raindrops

Abstract Drop–drop collision experiments were carried out at the Mainz vertical wind tunnel. Water drops of 2.5 mm diameter were freely floated at their terminal velocities in a vertical air stream and collided with 0.5 mm diameter droplets. The collisions were recorded with a high speed digital video camera at a frame rate of 1000 per second. Altogether 116 collision events were observed, 75 of which ended with coalescence, and the rest with filament type breakup. The coalescence efficiency and its dependence on the Weber number and on the eccentricity of the colliding drops showed good agreement with earlier numerical studies. Thirty-six recorded collisions were further analyzed in order …

The realization of autonomous, aircraft-based, real-time aerosol mass spectrometry in the upper troposphere and lower stratosphere (dataset)

Dataset accompanying the journal article titled "The realization of autonomous, aircraft-based, real-time aerosol mass spectrometry in the upper troposphere and lower stratosphere". Preprint: doi.org/10.5194/egusphere-2022-33

Chemical analysis of the Asian tropopause aerosol layer (ATAL) with emphasis on secondary aerosol particles using aircraft-based in situ aerosol mass spectrometry

Aircraft-borne in situ measurements of the chemical aerosol composition were conducted in the Asian tropopause aerosol layer (ATAL) over the Indian subcontinent in the summer of 2017, covering particle sizes below ∼3 µm. We have implemented a recently developed aerosol mass spectrometer, which adopts the laser desorption technique as well as the thermal desorption method for quantitative bulk information (i.e., a modified Aerodyne AMS), aboard the high-altitude research aircraft M-55 Geophysica. The instrument was deployed in July and August 2017 during the StratoClim EU campaign (Stratospheric and upper tropospheric processes for better Climate predictions) over Nepal, India, Bangladesh, a…

Application of an O-ring pinch device as a constant-pressure inlet (CPI) for airborne sampling

We present a novel and compact design of a constant-pressure inlet (CPI) developed for use in airborne aerosol mass spectrometry. In particular, the inlet system is optimized for aerodynamic lenses commonly used in aerosol mass spectrometers, in which efficient focusing of aerosol particles into a vacuum chamber requires a precisely controlled lens pressure, typically of a few hectopascals. The CPI device can also be used in condensation particle counters (CPCs), cloud condensation nucleus counters (CCNCs), and gas-phase sampling instruments across a wide range of altitudes and inlet pressures. The constant pressure is achieved by changing the inner diameter of a properly scaled O-ring that…

Chemical analysis of the Asian Tropopause Aerosol Layer (ATAL) with emphasis on secondary aerosol particles using aircraft based in situ aerosol mass spectrometry

Aircraft borne in-situ measurements of the chemical aerosol composition were conducted in the Asian Tropopause Aerosol layer (ATAL) over the Indian subcontinent in summer 2017 covering particle sizes below 3 µm. We have implemented a recently developed aerosol mass spectrometer, which adopts the laser desorption technique as well as the thermal desorption method for quantitative bulk information (i.e. a modified Aerodyne AMS), aboard the high altitude research aircraft M-55 Geophysica. The instrument was deployed in July and August 2017 during the StratoClim EU campaign (Stratospheric and upper tropospheric processes for better climate predictions) over Nepal, India, Bangladesh, and t…

Measurements of aerosol and CCN properties in the Mackenzie River delta (Arctic) during RACEPAC

Within the framework of the RACEPAC (Radiation-Aerosol-Cloud Experiment in the Arctic Circle) project, the Arctic aerosol, arriving at a ground-based station in Tuktoyaktuk (Mackenzie River delta area, Canada), was characterized during a period of 3 weeks in May 2014. Basic meteorological parameters and particle number size distributions (PNSDs) were observed and two distinct types of air masses were found. One type were typical Arctic haze air masses, termed accumulation-type air masses, characterized by a monomodal PNSD with a pronounced accumulation mode at sizes above 100 nm. These air masses were observed during a period when back trajectories indicate an air mass origin in the north-e…

The realization of autonomous, aircraft-based, real-time aerosol mass spectrometry in the upper troposphere and lower stratosphere

We report on the developments that enabled the field deployment of a fully automated aerosol mass spectrometer, especially designed for high-altitude measurements on unpressurized aircraft. The merits of the two main categories of real-time aerosol mass spectrometry, i.e. (a) single-particle laser desorption and ionization and (b) continuous thermal desorption and electron impact ionization of aerosols, have been integrated into one compact apparatus with the aim to perform in situ real-time analysis of aerosol chemical composition. The demonstrated instrument, named the ERICA (European Research Council Instrument for Chemical composition of Aerosols), operated successfully aboard the high-…

Application of an O-ring pinch device as a constant pressure inlet (CPI) for airborne sampling

We present a novel and compact design of a constant pressure inlet (CPI) developed for use in airborne aerosol mass spectrometry. In particular the inlet system is optimized for aerodynamic lenses commonly used in aerosol mass spectrometers, where efficient focusing of aerosol particles into a vacuum chamber requires a precisely controlled lens pressure, typically of a few hPa. The CPI device can also be used in gas phase sampling instruments in a large range of altitude and inlet pressure. The constant pressure is achieved by changing the inner diameter of a properly scaled O-ring that acts as a critical orifice. The CPI control keeps air pressure and thereby mass flow rate (≈&thinsp…

Aircraft-based observation of meteoric material in lower stratospheric aerosol particles between 15 and 68° N

In this paper we analyze aerosol particle composition measurements from five research missions conducted between 2014 and 2018 sampling the upper troposphere and lower stratosphere (UTLS), to assess the meridional extent of particles containing meteoric material. Additional data sets from a ground based study and from a low altitude aircraft mission are used to confirm the existence of meteoric material in lower tropospheric particles. Single particle laser ablation techniques with bipolar ion detection were used to measure the chemical composition of particles in a size range of approximately 150 nm to 3 μm. The five UTLS aircraft missions cover a latitude range from 15 to 68…