Simulation of global nucleation in the free troposphere and boundary layer based on direct measurements in the CERN CLOUD chamber
Abstract
All global models simulate particle formation based either on empirical relations derived from field campaigns or using rates based on extrapolation of thermodynamic and kinetic models. The difficulties associated with making laboratory measurements under atmospheric conditions mean that no global model predictions of particle formation have been based on directly measured rates. Here, we use nucleation rate measurements from the CERN cloud chamber for the sulphuric acid/ammonia system and the sulphuric acid/oxidised organic system to simulate particle formation in the GLOMAP global aerosol model. Measurements for the sulphuric acid/ammonia system cover a wide range of conditions of the free troposphere: temperatures of 208-298 K, sulphuric acid concentrations of <106-109 cm-3, ammonia concentrations of a few ppt to ~1 ppb, and ionisation rates for conditions between the lower and upper troposphere. In the organic experiments, a broad range of oxygenated compounds of biogenic origin was produced from oxidation of pinanediol (PD, C10H18O2), which is a first-generation oxidation product of α-pinene. The oxidation products can be considered as model compounds for oxidation products of biogenic monoterpenes. Based on the measurements, we developed rate expressions for the nucleation of sulphuric acid, ammonia and ions covering the whole troposphere, and for sulphuric acid and oxidised biogenic compounds in the boundary layer. We implemented these processes in a global aerosol microphysics model to assess their effect on new particle formation. We will present a comparison between the model results and ambient measurements of particle concentrations, including an assessment of the relative importance of the individual processes according to season, location and altitude.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.A51M..06D
- Keywords:
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- 0305 ATMOSPHERIC COMPOSITION AND STRUCTURE Aerosols and particles