Abstract
Abstract. New particle formation (NPF) is an important atmospheric phenomenon. During an NPF event, particles first form by nucleation and then grow further in size. The growth step is crucial because it controls the number of particles that can become cloud condensation nuclei. Among various physical and chemical processes contributing to particle growth, condensation by organic vapors has been suggested as important. In order to better understand the influence of biogenic emissions on particle growth, we carried out modeling studies of NPF events during the BEACHON-ROCS (Bio–hydro–atmosphere interactions of Energy, Aerosol, Carbon, H2O, Organics & Nitrogen – Rocky Mountain Organic Carbon Study) campaign at Manitou Experimental Forest Observatory in Colorado, USA. The site is representative of the semi-arid western USA. With the latest Criegee intermediate reaction rates implemented in the chemistry scheme, the model underestimates sulfuric acid concentration by 50 %, suggesting either missing sources of atmospheric sulfuric acid or an overestimated sink term. The results emphasize the contribution from biogenic volatile organic compound emissions to particle growth by demonstrating the effects of the oxidation products of monoterpenes and 2-Methyl-3-buten-2-ol (MBO). Monoterpene oxidation products are shown to influence the nighttime particle loadings significantly, while their concentrations are insufficient to grow the particles during the day. The growth of ultrafine particles in the daytime appears to be closely related to the OH oxidation products of MBO.
Highlights
Atmospheric aerosols have the potential to change the climate as they influence the Earth’s radiative balance as well as the hydrological cycle (e.g., Lohmann and Feichter, 2005; Kerminen et al, 2005)
In order to better understand the influence of biogenic emissions on particle growth, we carried out modeling studies of New particle formation (NPF) events during the BEACHON-ROCS (Bio– hydro–atmosphere interactions of Energy, Aerosol, Carbon, H2O, Organics & Nitrogen – Rocky Mountain Organic Carbon Study) campaign at Manitou Experimental Forest Observatory in Colorado, USA
The results emphasize the contribution from biogenic volatile organic compound emissions to particle growth by demonstrating the effects of the oxidation products of monoterpenes and 2-Methyl-3-buten2-ol (MBO)
Summary
Atmospheric aerosols have the potential to change the climate as they influence the Earth’s radiative balance as well as the hydrological cycle (e.g., Lohmann and Feichter, 2005; Kerminen et al, 2005). Apart from their climatic influences, aerosols reduce visibility and impact health. The nucleated particles grow further via various processes including condensation of vapors and coagulation (Kulmala et al, 2004a; Kulmala and Kerminen, 2008; Kerminen et al, 2010) This growth step determines the formation rate of detectable particles (usually > 3 nm) as well as the impact of NPF on cloud condensation nuclei populations (Kulmala et al, 2013). Organic compounds are the main drivers of the growth step and are critical for aerosol formation (Kerminen et al, 2000; Sellegri et al, 2005; Boy et al, 2005; Allan et al, 2006; Laaksonen et al, 2008; Ehn et al, 2014)
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