Microphysical and chemical characteristics of cloud droplet residuals and interstitial particles in continental stratocumulus clouds |
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| Institution: | 1. School of Earth, Atmospheric and Environmental Sciences, Centre for Atmospheric Science, University of Manchester, Manchester, United Kingdom;2. IGBP Secretariat, Royal Swedish Academy of Sciences, SE-10491, Stockholm, Sweden;3. Max-Planck Institute for Chemistry, Cloud Physics and Chemistry Department, Mainz, Germany;4. Department of Meteorology, Stockholm University, SE-10491, Stockholm, Sweden;5. Department of Applied Environmental Science, Stockholm University, SE-10491, Stockholm, Sweden;6. University of Mainz, Institute for Atmospheric Physics, Mainz, Germany;1. Joining and Welding Research Institute, Osaka University, 11-1, Mihogaoka, Ibaraki, Osaka 567-0047, Japan;2. Shanghai Toyo Tanso., Ltd., No. 486 Xinfei Road, Songjiang, Shanghai 201611, P.R. China;3. Advanced Carbon Technology Center, Toyo Tanso. Co., Ltd. 5-7-12, Takeshima, Nishiyodogawa-Ku, Osaka 555-0011, Japan;1. State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun 130012, China;2. Key Lab of Coherent Light, Atomic and Molecular Spectroscopy, Ministry of Education, Changchun 130012, China;1. U. S. Army Research Laboratory, 2800 Powder Mill Road, Adelphi, MD 20783, USA;2. Space Science Institute, 4750 Walnut Street, Boulder Suite 205, CO 80301, USA |
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| Abstract: | During June and July 2003 the Sources and Origins of Atmospheric Cloud Droplets experiment (SOACED) was carried out on a mountain-top site in central Sweden. The main objective of the experiment was to characterise the microphysical and chemical properties of cloud droplet residuals and interstitial aerosol particles in continental clouds and to understand the processes controlling cloud properties at this location.Interstitial and residual aerosol size distributions, cloud liquid water content and species- and size-resolved aerosol mass concentrations are the main variables employed to address questions pertaining to the cloud droplet number concentration and scavenging efficiency during a stratocumulus cloud event observed on July 28, 2003. In this cloud event, about 56% of the aerosol mass was associated with organic species, whilst SO4 accounted for 23% and NH4 for 14%. NO3 and Cl made up about 7% of the total mass.The partitioning of the aerosol particles between cloud droplets and interstitial air has been studied in terms of their microphysical properties. The scavenging efficiency, defined as the fraction of particles activated into cloud elements compared to the total amount of particles, was investigated as a function of size. The scavenging efficiency curves displayed different shapes during the cloud event, from an S-shaped curve, with low scavenging efficiency in the Aitken mode and larger scavenging efficiency in the accumulation mode, to more unusual shapes where Aitken-mode particles were either solely activated or activated in addition to accumulation-mode particles.This study suggests that alterations of the aerosol chemical composition occurred during the measurement period, changing the hygroscopic nature of the CCN and decreasing their activation diameter. It is also hypothesized that entrainment of drier air aloft may have introduced inhomogeneities in the supersaturation field and modified the S-shaped scavenging curves. |
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