Periodic Reporting for period 1 - CLOUD-DOC (CLOUD Doctoral Network)
Berichtszeitraum: 2022-09-01 bis 2024-08-31
The CLOUD-DOC MSCA DN is a multi-site network at twelve partner institutions across Europe. The network investigates the formation of aerosol particlesin the atmosphere, as well as various aspects of the interactions of cosmic rays with aerosols and clouds, which bears on the possibility of a "solar indirect" contribution to climate change. Besides the individual research of the doctoral candidates at their hosting institutions, the major focus of the network are sets of joint experiments carried out at CERN. These experiments are conducted at an aerosol chamber that is exposed to a CERN elementary particle beam where the effects of cosmic rays on aerosol and cloud formation can be efficiently simulated. The project integrates a suite of state of-the-art instruments developed for the analysis of atmospheric ions, trace gases, aerosols and ice particles. The chamber is optimized to study aerosol nucleation, growth and activation into clouds under precisely controlled conditions. The effects of cosmic ray ionization on these processes can be fully measured. An accelerator provides an adjustable and precisely measurable beam of artificial “cosmic rays” that closely matches natural cosmic rays spanning the atmospheric range from ground level to the maximum around 15 km altitude. Over the past years, the CLOUD facility was upgraded by adding a flow tube system (FLOTUS) that simulates multi-step multi-day atmospheric oxidation processes in a few minutes. Vapours generated in FLOTUS can then be transferred to the CLOUD chamber.
A large fraction of aerosol nucleation takes place in cold regions of the atmosphere that are extremely sensitive to particle concentrations, e.g. the tropical upper troposphere, the Arctic or the free troposphere above the Southern Ocean. NPF in these regions is considered to be the most urgent current topic in aerosol nucleation research. CLOUD has unique capabilities to study nucleation under cold conditions. In the CLOUD-DOC project we study nucleation and growth at low temperatures for several key chemical systems that are of high relevance for these regions.
In the CLOUD-DOC project all beneficiaries are part of the CLOUD experiment at CERN. The partners contribute a comprehensive set of research instrumentation to characterize the precursor gases, ions, oxidation products and their clusters, and aerosol particles. This is complemented by advanced modelling to understand the implications of the CLOUD measurements for climate.
A large fraction of aerosol nucleation takes place in cold regions of the atmosphere that are extremely sensitive to particle concentrations, e.g. the tropical upper troposphere, the Arctic or the free troposphere above the Southern Ocean. NPF in these regions is considered to be the most urgent current topic in aerosol nucleation research. CLOUD has unique capabilities to study nucleation under cold conditions. In the CLOUD-DOC project we study nucleation and growth at low temperatures for several key chemical systems that are of high relevance for these regions.
In the CLOUD-DOC project all beneficiaries are part of the CLOUD experiment at CERN. The partners contribute a comprehensive set of research instrumentation to characterize the precursor gases, ions, oxidation products and their clusters, and aerosol particles. This is complemented by advanced modelling to understand the implications of the CLOUD measurements for climate.
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).
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).
As a key result beyond state of the art, the paper by Shen et al. has been published in Nature in December 2024. It describes the highly efficient nucleation of isoprene oxidation products occurring in the upper troposphere above tropical forests such as the Amazon. Isoprene is identified as a forth chemical substance to drive atmospheric nucleation. Due to the very high biogenic emissions of isoprene in the tropics this is likely to be a major source of particle nucleation in the global troposphere. Nucleation rates, growth rates and the boosting effect of very small quantities of sulphuric or iodic acid for the nucleation rate are quantified. The chemical formation pathways from the OH oxidation of isoprene at very low temperatures are described. The particles formed in this way could represent a major source of cloud condensation nuclei in the tropical atmosphere. To this paper all twelve doctoral candidates contribute as co-authors, including DC Douglas Russell who has shared first authorship. This paper is an outstanding result considering the short time since the project started. These high-impact results were published two years into the project and just one year after the experiments took place. We plan to publish several follow-up studies in the remaining time of the project.