TY  - JOUR
A1  - Pöhlker, Mira L.
A1  - Pöhlker, Christopher
A1  - Ditas, Florian
A1  - Klimach, Thomas
A1  - Hrabe de Angelis, Isabella
A1  - Araújo, Alessandro
A1  - Brito, Joel
A1  - Carbone, Samara
A1  - Cheng, Yafang
A1  - Chi, Xuguang
A1  - Ditz, Reiner
A1  - Gunthe, Sachin S.
A1  - Kesselmeier, Jürgen
A1  - Könemann, Tobias
A1  - Lavrič, Jost-Valentin
A1  - Martin, Scot Turnbull
A1  - Mikhailov, Eugene
A1  - Moran-Zuloaga, Daniel
A1  - Rose, Diana
A1  - Saturno, Jorge
A1  - Su, Hang
A1  - Thalman, Ryan
A1  - Walter, David
A1  - Wang, Jian
A1  - Wolff, Stefan
A1  - Barbosa, Henrique M. J.
A1  - Artaxo, Paulo
A1  - Andreae, Meinrat O.
A1  - Pöschl, Ulrich
T1  - Long-term observations of cloud condensation nuclei in the Amazon rain forest – Part 1: Aerosol size distribution, hygroscopicity, and new model parametrizations for CCN prediction
T2  - Atmospheric chemistry and physics
N2  - Size-resolved long-term measurements of atmospheric aerosol and cloud condensation nuclei (CCN) concentrations and hygroscopicity were conducted at the remote Amazon Tall Tower Observatory (ATTO) in the central Amazon Basin over a 1-year period and full seasonal cycle (March 2014–February 2015). The measurements provide a climatology of CCN properties characteristic of a remote central Amazonian rain forest site.
The CCN measurements were continuously cycled through 10 levels of supersaturation (S   =  0.11 to 1.10 %) and span the aerosol particle size range from 20 to 245 nm. The mean critical diameters of CCN activation range from 43 nm at S  =  1.10 % to 172 nm at S  =  0.11 %. The particle hygroscopicity exhibits a pronounced size dependence with lower values for the Aitken mode (κAit  =  0.14 ± 0.03), higher values for the accumulation mode (κAcc  =  0.22 ± 0.05), and an overall mean value of κmean  =  0.17 ± 0.06, consistent with high fractions of organic aerosol.
The hygroscopicity parameter, κ, exhibits remarkably little temporal variability: no pronounced diurnal cycles, only weak seasonal trends, and few short-term variations during long-range transport events. In contrast, the CCN number concentrations exhibit a pronounced seasonal cycle, tracking the pollution-related seasonality in total aerosol concentration. We find that the variability in the CCN concentrations in the central Amazon is mostly driven by aerosol particle number concentration and size distribution, while variations in aerosol hygroscopicity and chemical composition matter only during a few episodes.
For modeling purposes, we compare different approaches of predicting CCN number concentration and present a novel parametrization, which allows accurate CCN predictions based on a small set of input data.
Y1  - 2016
UR  - http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/42622
UR  - https://nbn-resolving.org/urn:nbn:de:hebis:30:3-426226
SN  - 1680-7324
N1  - © Author(s) 2016. This work is distributed under the Creative Commons Attribution 3.0 License.
VL  - 16
SP  - 15709
EP  - 15740
PB  - European Geosciences Union
CY  - Katlenburg-Lindau.
ER  -