AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Simulation of Nucleation in the Global Atmosphere Based on CERN CLOUD Chamber Measurements
KEN CARSLAW, Eimear Dunne, Andreas Kuerten, Francesco Riccobono, Kamalika Sengupta, Catherine Scott, Joao Almeida, University of Leeds
Abstract Number: 462 Working Group: Advances in the Physics and Chemistry of New Particle Formation and Growth
Abstract Our understanding of global aerosol formation is based on models that use nucleation rates derived empirically from field campaigns or from extrapolation of thermodynamic and kinetic models. No global model predictions of particle formation throughout the atmosphere have been based on laboratory kinetic measurements. Here, we use nucleation rate measurements from the CERN cloud chamber for the sulfuric acid/ammonia system and the sulfuric acid/oxidized organic system to simulate particle formation throughout the troposphere using the GLOMAP global aerosol model. Measurements for the sulfuric acid/ammonia system cover a wide range of conditions of the free troposphere: temperatures of 208-298 K, sulfuric 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 (C10H18O2, a first-generation oxidation product of α-pinene), thus the compounds can be considered as representative of oxidation products of biogenic monoterpenes. The model predictions are in good agreement with measured particle concentrations. In the boundary layer, we show how our biogenically influenced nucleation rate can help to explain the observed seasonal cycle in particle concentrations. This behavior is not captured by a model that assumes that only sulfuric acid controls the rate, an assumption that is anyway ruled out by experimental results from CLOUD. Nevertheless, such a biogenic mechanism underpredicts particle concentrations outside the biologically active seasons, suggesting that ternary inorganic nucleation or other organic compounds contribute to nucleation rates.