As the core of the research activities the first CLOUD experiment was conducted at the CLOUD chamber in order to investigate the role of aerosol nucleation processes for atmospheric aerosols, clouds and climate. Comprehensive measurements of the precursor chemistry as well as the nucleation and initial growth rates were conducted for several chemical systems of interest, comprising individual experimental runs, systematically varying the experimental chamber conditions.
Particularly, the new particle formation under cold conditions were studied in these experiments as follows:
1. Upper free tropospheric aerosol nucleation and growth simulating the situation over the Amazon: We performed studies of upper free tropospheric new particle formation involving isoprene with and without sulphuric acid and with and without NOx at temperatures between -10◦C and -50◦C.
2. Upper free tropospheric nucleation and growth involving surfactants: Surprisingly high concentrations of long-chained fatty aldehydes have been reported at the Chacaltaya observatory in the Bolivian Andes (5200 m altitude). These surfactants originate from the surface of the tropical Pacific Ocean and, after convection, are transported long distances of up to 1000 km to reach the observatory, so their measured concentrations are highly diluted compared with those expected in the upper troposphere nearer their sources.
During the CLOUD experiment we studied the contributions of two fatty aldehydes (nonanal and dodecanal) to new particle formation and growth at temperatures between -15 ◦C and -50 ◦C. These experiments also included sulphuric acid and NOx.
3. Nucleation and growth in the Arctic: We studied new particle formation and growth involving dimethylsulphide, methanesulphonic acid (MSA), iodic acid and ammonia at concentrations found in the Arctic and at temperatures between 10 ◦C and -10 ◦C. The MSA was injected into CLOUD via FLOTUS to minimise the effect of high vapour concentrations of MSA and ammonia in nearby ‘plumes’ around their injection points before the vapours are well mixed. We included experiments to investigate the contribution of the dialdehyde glyoxal to particle growth via oligomerisation in the particle phase. Glyoxal is one of the most prevalent carbonyl compounds in the atmosphere.
All doctoral candidates (DCs) received comprehensive training on the preparation, operation, troubleshooting, and data analysis procedures for their individual instruments or models. Furthermore, they all learned to operate the complex CLOUD chamber for conducting the shifts during the experiments. As an exploitable result, an The prototype of a new mass spectrometic ion source and inlet is being developed by the DC of TOFWERK AG.
Overall, excellent progress has been achieved by all DCs. Some analyses already matured into paper manuscripts and published papers (see below).
