2009, Köppe, M., Hermann, M., Brenninkmeijer, C.A.M., Heintzenberg, J., Schlager, H., Schuck, T., Slemr, F., Sprung, D., van Velthoven, P.F.J., Wiedensohler, A., Zahn, A., Ziereis, H.

The origin of aerosol particles in the upper troposphere and lowermost stratosphere over the Eurasian continent was investigated by applying cluster analysis methods to in situ measured data. Number concentrations of submicrometer aerosol particles and trace gas mixing ratios derived by the CARIBIC (Civil Aircraft for Regular Investigation of the Atmosphere Based on an Instrument Container) measurement system on flights between Germany and South-East Asia were used for this analysis. Four cluster analysis methods were applied to a test data set and their capability of separating the data points into scientifically reasonable clusters was assessed. The best method was applied to seasonal data subsets for summer and winter resulting in five cluster or air mass types: stratosphere, tropopause, free troposphere, high clouds, and boundary layer influenced. Other source clusters, like aircraft emissions could not be resolved in the present data set with the used methods. While the cluster separation works satisfactory well for the summer data, in winter interpretation is more difficult, which is attributed to either different vertical transport pathways or different chemical lifetimes in both seasons. The geographical distribution of the clusters together with histograms for nucleation and Aitken mode particles within each cluster are presented. Aitken mode particle number concentrations show a clear vertical gradient with the lowest values in the lowermost stratosphere (750–2820 particles/cm3 STP, minimum of the two 25% – and maximum of the two 75%-percentiles of both seasons) and the highest values for the boundary-layer-influenced air (4290–22 760 particles/cm3 STP). Nucleation mode particles are also highest in the boundary-layer-influenced air (1260–29 500 particles/cm3 STP), but are lowest in the free troposphere (0–450 particles/cm3 STP). The given submicrometer particle number concentrations represent the first large-scale seasonal data sets for the upper troposphere and lowermost stratosphere over the Eurasian continent.

2007, Brenninkmeijer, C.A.M., Crutzen, P., Boumard, F., Dauer, T., Dix, B., Ebinghaus, R., Filippi, D., Fischer, H., Franke, H., Frieß, U., Heintzenberg, J., Helleis, F., Hermann, M., Kock, H.H., Koeppel, C., Lelieveld, J., Leuenberger, M., Martinsson, B.G., Miemczyk, S., Moret, H.P., Nguyen, H.N., Nyfeler, P., Oram, D., O'Sullivan, D., Penkett, S., Platt, U., Pupek, M., Ramonet, M., Randa, B., Reichelt, M., Rhee, T.S., Rohwer, J., Rosenfeld, K., Scharffe, D., Schlager, H., Schumann, U., Slemr, F., Sprung, D., Stock, P., Thaler, R., Valentino, F., van Velthoven, P., Waibel, A., Wandel, A., Waschitschek, K., Wiedensohler, A., Xueref-Remy, I., Zahn, A., Zech, U., Ziereis, H.

An airfreight container with automated instruments for measurement of atmospheric gases and trace compounds was operated on a monthly basis onboard a Boeing 767-300 ER of LTU International Airways during long-distance flights from 1997 to 2002 (CARIBIC, Civil Aircraft for Regular Investigation of the Atmosphere Based on an Instrument Container, http://www.caribic-atmospheric.com). Subsequently a more advanced system has been developed, using a larger capacity container with additional equipment and an improved inlet system. CARIBIC phase #2 was implemented on a new long-range aircraft type Airbus A340-600 of the Lufthansa German Airlines (Star Alliance) in December 2004, creating a powerful flying observatory. The instrument package comprises detectors for the measurement of O3, total and gaseous H2O, NO and NOy, CO, CO2, O2, Hg, and number concentrations of sub-micrometer particles (>4 nm, >12 nm, and >18 nm diameter). Furthermore, an optical particle counter (OPC) and a proton transfer mass spectrometer (PTR-MS) are incorporated. Aerosol samples are collected for analysis of elemental composition and particle morphology after flight. Air samples are taken in glass containers for laboratory analyses of hydrocarbons, halocarbons and greenhouse gases (including isotopic composition of CO2) in several laboratories. Absorption tubes collect oxygenated volatile organic compounds. Three differential optical absorption spectrometers (DOAS) with their telescopes mounted in the inlet system measure atmospheric trace gases such as BrO, HONO, and NO2. A video camera mounted in the inlet provides information about clouds along the flight track. The flying observatory, its equipment and examples of measurement results are reported.

2017, Leck, C., Bigg, E.K., Covert, D.S., Heintzenberg, J., Maenhaut, W., Nilsson, E.D., Wiedensohler, A.

The broad aim of the Atmospheric program of the International Arctic Ocean Expedition (IAOE-91) was to test the hypothesis that marine biogenically produced dimethyl sulfide (DMS) gas can exert a significant global climatic control. The hypothesis states that DMS is transferred to the atmosphere and is oxidised to form airborne particles. Some of these grow large enough to act as cloud condensation nuclei (CCN) which help determine cloud droplet concentration. The latter has a strong influence on cloud albedo and hence on the radiation balance of the area affected. In summer, the central Arctic is a specially favourable region for studying the natural sulfur cycle in that the open waters surrounding the pack ice are the only significant sources of DMS and there are almost no anthropogenic particle sources. Concentrations of seawater and atmospheric DMS decreased at about the same rate during the period of measurements, (1 August to 6 October, latitudes 75°N to 90°N) spanning about three orders of magnitude. Methane sulfonate and nonsea salt sulfate in the submicrometer particles, which may be derived from atmospheric DMS, also decreased similarly, suggesting that the first part of the hypothesis under test was true. Influences on cloud droplet concentration and radiation balance could not be measured. Size-resolved aerosol chemistry showed a much lower proportion of methane sulfonate to be associated with supermicrometer particles than has been found elsewhere. Its molar ratio to nonsea salt sulfate suggested that the processes controlling the particulate chemistry do not exhibit a net temperature dependence. Elemental analysis of the aerosol also revealed the interesting possibility that debris from Siberian rivers transported on the moving ice represent a fairly widespread source of supermicrometer crustal material within the pack ice. Highly resolved measurements of aerosol number size distributions were made in the diameter range 3 nm to 500 nm. 3 distinct modal sizes were usually present, the “ultrafine”, “Aitken” and “accumulation” modes centred on 14, 45 and 170 nm diameter, respectively. The presence of ultrafine particles, implying recent production, was more frequent than has been found in lower latitude remote marine areas. Evidence suggests that they were mixed to the surface from higher levels. Sudden and often drastic changes in aerosol concentration and size distribution were surprisingly frequent in view of the relatively slowly changing meteorology of the central Arctic during the study period and the absence of strong pollution sources. They were most common in particles likely to have taken part in cloud formation (> 80 nm diameter). 2 factors appear to have been involved in these sudden changes. The 1st was the formation of vertical gradients in aerosol concentration due to interactions between particles and clouds or favoured regions for new particle production during periods of stability. The 2nd was sporadic localised breakdowns of the stability, bringing changed particle concentrations to the measurement level. Probable reasons for these sporadic mixing events were indicated by the structure of the Marine Boundary Layer (MBL) investigated with high resolution rawinsondes. Low level jets were present about 60% of the time, producing conditions conductive to turbulence and shear-induced waves. It is concluded that an even more detailed study of meteorological processes in the MBL in conjunction with more highly time-resolved measurements of gas-aerosol physics and chemistry appears to be essential in any future research aimed at studying the indirect, cloud mediated, effect of aerosol particles.

2018, Wiedensohler, A., Ma, N., Birmili, W., Heintzenberg, J., Ditas, F., Andreae, M.O., Panov, A.

Aerosol particle number size distributions (PNSD) were investigated to verify, if extremely low-volatility organic vapors (ELVOC) from natural sources alone could induce new particle formation and growth events over the remote boreal forest region of Siberia, hundreds of kilometers away from significant anthropogenic sources. We re-evaluated observations determined at a height of 300 m of the remote observatory ZOTTO (Zotino Tall Tower Observatory, http://www.zottoproject.org). We found that new particle formation events occurred only on 11 days in a 3-year period, suggesting that homogeneous nucleation with a subsequent condensational growth could not be the major process, maintaining the particle number concentration in the planetary boundary layer of the remote boreal forest area of Siberia. © 2018 Elsevier Ltd

1996, Covert, D.S., Wiedensohler, A., Aalto, P., Heintzenberg, J., Mcmurry, P.H., Leck, C.

Aerosol physics measurements made onboard the Swedish icebreaker Oden in the late Summer and early Autumn of 1991 during the International Arctic Ocean Expedition (IAOE-91) have provided the first data on the size distribution of particles in the Arctic marine boundary layer (MBL) that cover both the number and mass modes of the size range from 3 to 500 nm diameter. These measurements were made in conjunction with atmospheric gas and condensed phase chemistry measurements in an effort to understand a part of the ocean-atmosphere sulfur cycle. Analysis of the particle physics data showed that there were three distinct number modes in the submicrometric aerosol in the Arctic MBL. These modes had geometric mean diameters of around 170 nm. 45 nm and 14 nm referred to as accumulation, Aitken and ultrafine modes, respectively. There were clear minima in number concentrations between the modes that appeared at 20 to 30 nm and at 80 to 100 nm. The total number concentration was most frequently between 30 and 60 particles cm-3 with a mean value of around 100 particles cm-3, but the hourly average concentration varied over two to three orders of magnitude during the 70 days of the expedition. On average, the highest concentration was in the accumulation mode that contained about 45% of the total number, while the Aitken mode contained about 40%. The greatest variability was in the ultrafine mode concentration which is indicative of active, earby sources (nucleation from the gas phase) and sinks; the Aitken and accumulation mode concentrations were much less variable. The ultrafine mode was observed about two thirds of the time and was dominant 10% of the time. A detailed description and statistical analysis of the modal aerosol parameters is presented here.

2003, Stratmann, F., Siebert, H., Spindler, G., Wehner, B., Althausen, D., Heintzenberg, J., Hellmuth, O., Rinke, R., Schmieder, U., Seidel, C., Tuch, T., Uhrner, U., Wiedensohler, A., Wandinger, U., Wendisch, M., Schell, D., Stohl, A.

During the SATURN experiment, which took place from 27 May to 14 June 2002, new particle formation in the continental boundary layer was investigated. Simultaneous ground-based and tethered-balloon-borne measurements were performed, including meteorological parameters, particle number concentrations and size distributions, gaseous precursor concentrations and SODAR and LIDAR observations. Newly formed particles were observed inside the residual layer, before the break-up process of the nocturnal inversion, and inside the mixing layer throughout the break-up of the nocturnal inversion and during the evolution of the planetary boundary layer.

2017, Hermann, M., Brenninkmeijer, C.A.M., Slemr, F., Heintzenberg, J., Martinsson, B.G., Schlager, H., Van Velthoven, P.F.J., Wiedensohler, A., Zahn, A., Ziereis, H.

Particle number and mass concentrations of submicrometer aerosol particles were determined for the upper troposphere over the mid-latitude North Atlantic within the Civil Aircraft for Regular Investigation of the Atmosphere Based on an Instrument Container project (CARIBIC, http://www.caribic-atmospheric.com). Between May 2001 and April 2002, 22 flights from Germany to the Caribbean were conducted using an automated measurement container on a B767 passenger aircraft. Spatial and seasonal probability distributions for ultrafine and Aitken mode particles as well as mass concentrations of particulate sulphur in 8–12 km altitude are presented. High particle number concentrations (mostly 2500–15 000 particles cm-3 STP) are particularly found in summer over the western North Atlantic Ocean close to the North American continent. The distributions together with an analysis of particle source processes show that deep vertical transport is the dominant process leading to most of the events with high particle number concentrations (8000 particles cm-3 STP) for ultrafine particles as well as for Aitken mode particles. This study emphasizes the importance of deep vertical transport and cloud processing for the concentration of aerosol particles in the upper troposphere.