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- ItemChemical composition and droplet size distribution of cloud at the summit of Mount Tai, China(Katlenburg-Lindau : EGU, 2017) Li, Jiarong; Wang, Xinfeng; Chen, Jianmin; Zhu, Chao; Li, Weijun; Li, Chengbao; Liu, Lu; Xu, Caihong; Wen, Liang; Xue, Likun; Wang, Wenxing; Ding, Aijun; Herrmann, HartmutThe chemical composition of 39 cloud samples and droplet size distributions in 24 cloud events were investigated at the summit of Mt. Tai from July to October 2014. Inorganic ions, organic acids, metals, HCHO, H2O2, sulfur( IV), organic carbon, and elemental carbon as well as pH and electrical conductivity were analyzed. The acidity of the cloud water significantly decreased from a reported value of pH 3.86 during 2007-2008 (Guo et al., 2012) to pH 5.87 in the present study. The concentrations of nitrate and ammonium were both increased since 2007-2008, but the overcompensation of ammonium led to an increase in the mean pH value. The microphysical properties showed that cloud droplets were smaller than 26.0 μm and most were in the range of 6.0-9.0 μm at Mt. Tai. The maximum droplet number concentration (Nd) was associated with a droplet size of 7.0 μm. High liquid water content (LWC) values could facilitate the formation of larger cloud droplets and broadened the droplet size distribution. Cloud droplets exhibited a strong interaction with atmospheric aerosols. Higher PM2.5 levels resulted in higher concentrations of water-soluble ions and smaller sizes with increased numbers of cloud droplets. The lower pH values were likely to occur at higher PM2.5 concentrations. Clouds were an important sink for soluble materials in the atmosphere. The dilution effect of cloud water should be considered when estimating concentrations of soluble components in the cloud phase.
- ItemMarine organic matter in the remote environment of the Cape Verde islands-an introduction and overview to the MarParCloud campaign(Katlenburg-Lindau : EGU, 2020) van Pinxteren, Manuela; Fomba, KhannehWadinga; Triesch, Nadja; Stolle, Christian; Wurl, Oliver; Bahlmann, Enno; Gong, Xianda; Voigtländer, Jens; Wex, Heike; Robinson, Tiera-Brandy; Barthel, Stefan; Zeppenfeld, Sebastian; Hoffmann, Erik Hans; Roveretto, Marie; Li, Chunlin; Grosselin, Benoit; Daële, Veronique; Senf, Fabian; van Pinxteren, Dominik; Manzi, Malena; Zabalegui, Nicolás; Frka, Sanja; Gašparović, Blaženka; Pereira, Ryan; Li, Tao; Wen, Liang; Li, Jiarong; Zhu, Chao; Chen, Hui; Chen, Jianmin; Fiedler, Björn; von Tümpling, Wolf; Read, Katie Alana; Punjabi, Shalini; Lewis, Alastair Charles; Hopkins, James Roland; Carpenter, Lucy Jane; Peeken, Ilka; Rixen, Tim; Schulz-Bull, Detlef; Mong, María Eugenia; Mellouki, Abdelwahid; George, Christian; Stratmann, Frank; Herrmann, HartmutThe project MarParCloud (Marine biological production, organic aerosol Particles and marine Clouds: a process chain) aims to improve our understanding of the genesis, modification and impact of marine organic matter (OM) from its biological production, to its export to marine aerosol particles and, finally, to its ability to act as ice-nucleating particles (INPs) and cloud condensation nuclei (CCN). A field campaign at the Cape Verde Atmospheric Observatory (CVAO) in the tropics in September-October 2017 formed the core of this project that was jointly performed with the project MARSU (MARine atmospheric Science Unravelled). A suite of chemical, physical, biological and meteorological techniques was applied, and comprehensive measurements of bulk water, the sea surface microlayer (SML), cloud water and ambient aerosol particles collected at a ground-based and a mountain station took place. Key variables comprised the chemical characterization of the atmospherically relevant OM components in the ocean and the atmosphere as well as measurements of INPs and CCN. Moreover, bacterial cell counts, mercury species and trace gases were analyzed. To interpret the results, the measurements were accompanied by various auxiliary parameters such as air mass back-trajectory analysis, vertical atmospheric profile analysis, cloud observations and pigment measurements in seawater. Additional modeling studies supported the experimental analysis. During the campaign, the CVAO exhibited marine air masses with low and partly moderate dust influences. The marine boundary layer was well mixed as indicated by an almost uniform particle number size distribution within the boundary layer. Lipid biomarkers were present in the aerosol particles in typical concentrations of marine background conditions. Accumulation-and coarse-mode particles served as CCN and were efficiently transferred to the cloud water. The ascent of ocean-derived compounds, such as sea salt and sugar-like compounds, to the cloud level, as derived from chemical analysis and atmospheric transfer modeling results, denotes an influence of marine emissions on cloud formation. Organic nitrogen compounds (free amino acids) were enriched by several orders of magnitude in submicron aerosol particles and in cloud water compared to seawater. However, INP measurements also indicated a significant contribution of other non-marine sources to the local INP concentration, as (biologically active) INPs were mainly present in supermicron aerosol particles that are not suggested to undergo strong enrichment during ocean-atmosphere transfer. In addition, the number of CCN at the supersaturation of 0.30 % was about 2.5 times higher during dust periods compared to marine periods. Lipids, sugar-like compounds, UV-absorbing (UV: ultraviolet) humic-like substances and low-molecularweight neutral components were important organic compounds in the seawater, and highly surface-active lipids were enriched within the SML. The selective enrichment of specific organic compounds in the SML needs to be studied in further detail and implemented in an OM source function for emission modeling to better understand transfer patterns, the mechanisms of marine OM transformation in the atmosphere and the role of additional sources. In summary, when looking at particulate mass, we see oceanic compounds transferred to the atmospheric aerosol and to the cloud level, while from a perspective of particle number concentrations, sea spray aerosol (i.e., primary marine aerosol) contributions to both CCN and INPs are rather limited. © Author(s) 2020.