Abstract
Abstract. The particle formation scheme within PMCAMx-UF, a three-dimensional chemical transport model, was updated with particle formation rates for the ternary H2SO4–NH3–H2O pathway simulated by the Atmospheric Cluster Dynamics Code (ACDC) using quantum chemical input data. The model was applied over Europe for May 2008, during which the EUCAARI-LONGREX (European Aerosol Cloud Climate and Air Quality Interactions–Long-Range Experiment) campaign was carried out, providing aircraft vertical profiles of aerosol number concentrations. The updated model reproduces the observed number concentrations of particles larger than 4 nm within 1 order of magnitude throughout the atmospheric column. This agreement is encouraging considering the fact that no semi-empirical fitting was needed to obtain realistic particle formation rates. The cloud adjustment scheme for modifying the photolysis rate profiles within PMCAMx-UF was also updated with the TUV (Tropospheric Ultraviolet and Visible) radiative-transfer model. Results show that, although the effect of the new cloud adjustment scheme on total number concentrations is small, enhanced new-particle formation is predicted near cloudy regions. This is due to the enhanced radiation above and in the vicinity of the clouds, which in turn leads to higher production of sulfuric acid. The sensitivity of the results to including emissions from natural sources is also discussed.
Highlights
Formation of new particles from atmospheric vapors is potentially an important source of particulate matter in the atmosphere, especially in the ultrafine (< 100 nm in diameter) size range (Kulmala et al, 2004; Merikanto et al, 2009; Jung et al, 2010; Fountoukis et al, 2012; Kerminen et al, 2012; Fuzzi et al, 2015)
In this work we describe the implementation of a H2SO4– H2O–NH3 new-particle formation scheme based on the output of the Atmospheric Cluster Dynamics Code (ACDC) model to the regional chemical transport model PMCAMx-UF (Jung et al, 2010; Fountoukis et al, 2012)
In this study we explore the sensitivity of PMCAMx-UF to cases (1) with an updated NPF scheme with ACDCbased formation rates, (2) with an updated cloud adjustment scheme with TUV implementation, and (3) including natural www.geosci-model-dev.net/9/2741/2016/
Summary
Formation of new particles from atmospheric vapors (newparticle formation, NPF) is potentially an important source of particulate matter in the atmosphere, especially in the ultrafine (< 100 nm in diameter) size range (Kulmala et al, 2004; Merikanto et al, 2009; Jung et al, 2010; Fountoukis et al, 2012; Kerminen et al, 2012; Fuzzi et al, 2015). In modeling studies on the role of in situ NPF as a particle source, particle formation has been represented with various parameterizations including binary (Vehkamäki et al, 2002) or ternary (Napari et al, 2002) nucleation based on the classical nucleation theory (CNT), semi-empirical activation (Kulmala et al, 2006), kinetic (McMurry, 1980) or organic-enhanced (Paasonen et al, 2010) NPF, and/or ionmediated nucleation (Yu and Luo, 2009) These parameterizations have generally assumed sulfuric acid (H2SO4), water (H2O), ammonia (NH3), or different organic species as the compounds forming the new particles. In many previous studies (Spracklen et al, 2006; Makkonen et al, 2009; Yu et al, 2010) the binary H2SO4–H2O nucleation has been assumed to dominate in the upper atmosphere and be negligible at lower altitudes, and it has often been superimposed with one of the other mechanisms
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