Abstract
Abstract. The Atmospheric Cluster Dynamics Code (ACDC) is presented and explored. This program was created to study the first steps of atmospheric new particle formation by examining the formation of molecular clusters from atmospherically relevant molecules. The program models the cluster kinetics by explicit solution of the birth–death equations, using an efficient computer script for their generation and the MATLAB ode15s routine for their solution. Through the use of evaporation rate coefficients derived from formation free energies calculated by quantum chemical methods for clusters containing dimethylamine or ammonia and sulphuric acid, we have explored the effect of changing various parameters at atmospherically relevant monomer concentrations. We have included in our model clusters with 0–4 base molecules and 0–4 sulfuric acid molecules for which we have commensurable quantum chemical data. The tests demonstrate that large effects can be seen for even small changes in different parameters, due to the non-linearity of the system. In particular, changing the temperature had a significant impact on the steady-state concentrations of all clusters, while the boundary effects (allowing clusters to grow to sizes beyond the largest cluster that the code keeps track of, or forbidding such processes), coagulation sink terms, non-monomer collisions, sticking probabilities and monomer concentrations did not show as large effects under the conditions studied. Removal of coagulation sink terms prevented the system from reaching the steady state when all the initial cluster concentrations were set to the default value of 1 m−3, which is probably an effect caused by studying only relatively small cluster sizes.
Highlights
Atmospheric aerosol particles are known to have significant effects on both the global climate and human health (Poschl, 2005)
If we take the DMA concentration to be equal to 5 × 1013 m−3, Atmospheric Cluster Dynamics Code (ACDC) predicts a particle formation rate of around 106 m−3 s−1, which is a typical new particle formation rate seen in Hyytiala (Dal Maso et al, 2005; Manninen et al, 2009)
We have presented a new program for modeling the kinetics of clusters by explicit solution of the birth–death equations, using an efficient computer script for their generation and the MATLAB ode15s routine for their solution
Summary
Atmospheric aerosol particles are known to have significant effects on both the global climate and human health (Poschl, 2005). Secondary aerosols form as a result of a series of events, starting with the clustering of individual molecules and progressing through growth into stable particles (Kulmala, 2003). Atmospheric particle formation has been observed to occur across a wide range of climates and environments (Kulmala et al, 2004), but probing the initial steps (where clusters measure one nanometer across or less) is still difficult, despite recent advances in instruments to measure both ionic and neutral clusters of very small size (Hirsikko et al, 2011; Vanhanen et al, 2011; Sipilaet al., 2009, 2010; Petajaet al., 2011). Experimental and theoretical studies indicate that atmospheric particle formation involves sulfuric acid and water (see, for example, Brus et al (2011) and references therein), but these two components are not enough to explain all the observed particle formation events. Courtney (1962) explicitly solved the BDE equations for clusters up to one hundred molecules of water. Nishioka and Fujita (1994) looked at the binary water/sulfuric acid
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
