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- ItemNew particle formation and its effect on cloud condensation nuclei abundance in the summer Arctic: A case study in the Fram Strait and Barents Sea(Katlenburg-Lindau : EGU, 2019) Kecorius, Simonas; Vogl, Teresa; Paasonen, Pauli; Lampilahti, Janne; Rothenberg, Daniel; Wex, Heike; Zeppenfeld, Sebastian; van Pinxteren, Manuela; Hartmann, Markus; Henning, Silvia; Gong, Xianda; Welti, Andre; Kulmala, Markku; Stratmann, Frank; Herrmann, Hartmut; Wiedensohler, AlfredIn a warming Arctic the increased occurrence of new particle formation (NPF) is believed to originate from the declining ice coverage during summertime. Understanding the physico-chemical properties of newly formed particles, as well as mechanisms that control both particle formation and growth in this pristine environment, is important for interpreting aerosol-cloud interactions, to which the Arctic climate can be highly sensitive. In this investigation, we present the analysis of NPF and growth in the high summer Arctic. The measurements were made on-board research vessel Polarstern during the PS106 Arctic expedition. Four distinctive NPF and subsequent particle growth events were observed, during which particle (diameter in a range 10-50 nm) number concentrations increased from background values of approx. 40 up to 4000 cm-3. Based on particle formation and growth rates, as well as hygroscopicity of nucleation and the Aitken mode particles, we distinguished two different types of NPF events. First, some NPF events were favored by negative ions, resulting in more-hygroscopic nucleation mode particles and suggesting sulfuric acid as a precursor gas. Second, other NPF events resulted in less-hygroscopic particles, indicating the influence of organic vapors on particle formation and growth. To test the climatic relevance of NPF and its influence on the cloud condensation nuclei (CCN) budget in the Arctic, we applied a zero-dimensional, adiabatic cloud parcel model. At an updraft velocity of 0.1 m s-1, the particle number size distribution (PNSD) generated during nucleation processes resulted in an increase in the CCN number concentration by a factor of 2 to 5 compared to the background CCN concentrations. This result was confirmed by the directly measured CCN number concentrations. Although particles did not grow beyond 50 nm in diameter and the activated fraction of 15-50 nm particles was on average below 10 %, it could be shown that the sheer number of particles produced by the nucleation process is enough to significantly influence the background CCN number concentration. This implies that NPF can be an important source of CCN in the Arctic. However, more studies should be conducted in the future to understand mechanisms of NPF, sources of precursor gases and condensable vapors, as well as the role of the aged nucleation mode particles in Arctic cloud formation. © Author(s) 2019. This work is distributed under the Creative Commons Attribution 4.0 License.
- ItemInfluence of biomass burning on mixing state of sub-micron aerosol particles in the North China Plain(Oxford [u.a.] : Elsevier, 2017) Kecorius, Simonas; Ma, Nan; Teich, Monique; van Pinxteren, Dominik; Zhang, Shenglan; Gröβ, Johannes; Spindler, Gerald; Müller, Konrad; Iinuma, Yoshiteru; Hu, Min; Herrmann, Hartmut; Wiedensohler, AlfredParticulate emissions from crop residue burning decrease the air quality as well as influence aerosol radiative properties on a regional scale. The North China Plain (NCP) is known for the large scale biomass burning (BB) of field residues, which often results in heavy haze pollution episodes across the region. We have been able to capture a unique BB episode during the international CAREBeijing-NCP intensive field campaign in Wangdu in the NCP (38.6°N, 115.2°E) from June to July 2014. It was found that aerosol particles originating from this BB event showed a significantly different mixing state compared with clean and non-BB pollution episodes. BB originated particles showed a narrower probability density function (PDF) of shrink factor (SF). And the maximum was found at shrink factor of 0.6, which is higher than in other episodes. The non-volatile particle number fraction during the BB episode decreased to 3% and was the lowest measured value compared to all other predefined episodes. To evaluate the influence of particle mixing state on aerosol single scattering albedo (SSA), SSA at different RHs was simulated using the measured aerosol physical-chemical properties. The differences between the calculated SSA for biomass burning, clean and pollution episodes are significant, meaning that the variation of SSA in different pollution conditions needs to be considered in the evaluation of aerosol direct radiative effects in the NCP. And the calculated SSA was found to be quite sensitive on the mixing state of BC, especially at low-RH condition. The simulated SSA was also compared with the measured values. For all the three predefined episodes, the measured SSA are very close to the calculated ones with assumed mixing states of homogeneously internal and core-shell internal mixing, indicating that both of the conception models are appropriate for the calculation of ambient SSA in the NCP.
- ItemVariation of CCN activity during new particle formation events in the North China Plain(München : European Geopyhsical Union, 2016) Ma, Nan; Zhao, Chunsheng; Tao, Jiangchuan; Wu, Zhijun; Kecorius, Simonas; Wang, Zhibin; Größ, Johannes; Liu, Hongjian; Bian, Yuxuan; Kuang, Ye; Teich, Monique; Spindler, Gerald; Müller, Konrad; van Pinxteren, Dominik; Herrmann, Hartmut; Hu, Min; Wiedensohler, AlfredThe aim of this investigation was to obtain a better understanding of the variability of the cloud condensation nuclei (CCN) activity during new particle formation (NPF) events in an anthropogenically polluted atmosphere of the North China Plain (NCP). We investigated the size-resolved activation ratio as well as particle number size distribution, hygroscopicity, and volatility during a 4-week intensive field experiment in summertime at a regional atmospheric observatory in Xianghe. Interestingly, based on a case study, two types of NPF events were found, in which the newly formed particles exhibited either a higher or a lower hygroscopicity. Therefore, the CCN activity of newly formed particles in different NPF events was largely different, indicating that a simple parameterization of particle CCN activity during NPF events over the NCP might lead to poor estimates of CCN number concentration (NCCN). For a more accurate estimation of the potential NCCN during NPF events, the variation of CCN activity has to be taken into account. Considering that a fixed activation ratio curve or critical diameter are usually used to calculate NCCN, the influence of the variation of particle CCN activity on the calculation of NCCN during NPF events was evaluated based on the two parameterizations. It was found that NCCN might be underestimated by up to 30 % if a single activation ratio curve (representative of the region and season) were to be used in the calculation; and might be underestimated by up to 50 % if a fixed critical diameter (representative of the region and season) were used. Therefore, we suggest not using a fixed critical diameter in the prediction of NCCN in NPF. If real-time CCN activity data are not available, using a proper fixed activation ratio curve can be an alternative but compromised choice.
- ItemThe Arctic Cloud Puzzle: Using ACLOUD/PASCAL Multiplatform Observations to Unravel the Role of Clouds and Aerosol Particles in Arctic Amplification(Boston, Mass. : ASM, 2019) Wendisch, Manfred; Macke, Andreas; Ehrlich, André; Lüpkes, Christof; Mech, Mario; Chechin, Dmitry; Dethloff, Klaus; Velasco, Carola Barrientos; Bozem, Heiko; Brückner, Marlen; Clemen, Hans-Christian; Crewell, Susanne; Donth, Tobias; Dupuy, Regis; Ebell, Kerstin; Egerer, Ulrike; Engelmann, Ronny; Engler, Christa; Eppers, Oliver; Gehrmann, Martin; Gong, Xianda; Gottschalk, Matthias; Gourbeyre, Christophe; Griesche, Hannes; Hartmann, Jörg; Hartmann, Markus; Heinold, Bernd; Herber, Andreas; Herrmann, Hartmut; Heygster, Georg; Hoor, Peter; Jafariserajehlou, Soheila; Jäkel, Evelyn; Järvinen, Emma; Jourdan, Olivier; Kästner, Udo; Kecorius, Simonas; Knudsen, Erlend M.; Köllner, Franziska; Kretzschmar, Jan; Lelli, Luca; Leroy, Delphine; Maturilli, Marion; Mei, Linlu; Mertes, Stephan; Mioche, Guillaume; Neuber, Roland; Nicolaus, Marcel; Nomokonova, Tatiana; Notholt, Justus; Palm, Mathias; van Pinxteren, Manuela; Quaas, Johannes; Richter, Philipp; Ruiz-Donoso, Elena; Schäfer, Michael; Schmieder, Katja; Schnaiter, Martin; Schneider, Johannes; Schwarzenböck, Alfons; Seifert, Patric; Shupe, Matthew D.; Siebert, Holger; Spreen, Gunnar; Stapf, Johannes; Stratmann, Frank; Vogl, Teresa; Welti, André; Wex, Heike; Wiedensohler, Alfred; Zanatta, Marco; Zeppenfeld, SebastianClouds play an important role in Arctic amplification. This term represents the recently observed enhanced warming of the Arctic relative to the global increase of near-surface air temperature. However, there are still important knowledge gaps regarding the interplay between Arctic clouds and aerosol particles, and surface properties, as well as turbulent and radiative fluxes that inhibit accurate model simulations of clouds in the Arctic climate system. In an attempt to resolve this so-called Arctic cloud puzzle, two comprehensive and closely coordinated field studies were conducted: the Arctic Cloud Observations Using Airborne Measurements during Polar Day (ACLOUD) aircraft campaign and the Physical Feedbacks of Arctic Boundary Layer, Sea Ice, Cloud and Aerosol (PASCAL) ice breaker expedition. Both observational studies were performed in the framework of the German Arctic Amplification: Climate Relevant Atmospheric and Surface Processes, and Feedback Mechanisms (AC) project. They took place in the vicinity of Svalbard, Norway, in May and June 2017. ACLOUD and PASCAL explored four pieces of the Arctic cloud puzzle: cloud properties, aerosol impact on clouds, atmospheric radiation, and turbulent dynamical processes. The two instrumented Polar 5 and Polar 6 aircraft; the icebreaker Research Vessel (R/V) Polarstern; an ice floe camp including an instrumented tethered balloon; and the permanent ground-based measurement station at Ny-Ålesund, Svalbard, were employed to observe Arctic low- and mid-level mixed-phase clouds and to investigate related atmospheric and surface processes. The Polar 5 aircraft served as a remote sensing observatory examining the clouds from above by downward-looking sensors; the Polar 6 aircraft operated as a flying in situ measurement laboratory sampling inside and below the clouds. Most of the collocated Polar 5/6 flights were conducted either above the R/V Polarstern or over the Ny-Ålesund station, both of which monitored the clouds from below using similar but upward-looking remote sensing techniques as the Polar 5 aircraft. Several of the flights were carried out underneath collocated satellite tracks. The paper motivates the scientific objectives of the ACLOUD/PASCAL observations and describes the measured quantities, retrieved parameters, and the applied complementary instrumentation. Furthermore, it discusses selected measurement results and poses critical research questions to be answered in future papers analyzing the data from the two field campaigns.