Canadian Aerosol Module: A size‐segregated simulation of atmospheric aerosol processes for climate and air quality models 1. Module development

Abstract

[1] A size-segregated multicomponent aerosol algorithm, the Canadian Aerosol Module (CAM), was developed for use with climate and air quality models. It includes major aerosol processes in the atmosphere: generation, hygroscopic growth, coagulation, nucleation, condensation, dry deposition/sedimentation, below-cloud scavenging, aerosol activation, a cloud module with explicit microphysical processes to treat aerosol-cloud interactions and chemical transformation of sulphur species in clear air and in clouds. The numerical solution was optimized to efficiently solve the complicated size-segregated multicomponent aerosol system and make it feasible to be included in global and regional models. An internal mixture is assumed for all types of aerosols except for soil dust and black carbon which are assumed to be externally mixed close to sources. To test the algorithm, emissions to the atmosphere of anthropogenic and natural aerosols are simulated for two aerosol types: sea salt and sulphate. A comparison was made of two numerical solutions of the aerosol algorithm: process splitting and ordinary differential equation (ODE) solver. It was found that the process-splitting method used for this model is within 15% of the more accurate ODE solution for the total sulphate mass concentration and <1% accurate for sea-salt concentration. Furthermore, it is computationally more than 100 times faster. The sensitivity of the simulated size distributions to the number of size bins was also investigated. The diffusional behavior of each individual process was quantitatively characterized by the difference in the mode radius and standard deviation of a lognormal curve fit of distributions between the approximate solution and the 96-bin reference solution. Both the number and mass size distributions were adequately predicted by a sectional model of 12 bins in many situations in the atmosphere where the sink for condensable matter on existing aerosol surface area is high enough that nucleation of new particles is negligible. Total mass concentration was adequately simulated using lower size resolution of 8 bins. However, to properly resolve nucleation mode size distributions and minimize the numerical diffusion, a sectional model of 18 size bins or greater is needed. The number of size bins is more important in resolving the nucleation mode peaks than in reducing the diffusional behavior of aerosol processes. Application of CAM in a study of the global cycling of sea-salt mass accompanies this paper [Gong et al., 2002].

Assessment of the dehydration‐greenhouse feedback over the Arctic during February 1990

“…NARCM simulates aerosol explicitly with 12 size bins from 0.005 to 20.48 µm (Gong et al, 2003). The aerosol module CAM is a size-segregated multi-component algorithm that treats five major types of aerosols: sea-salt, sulfate, black carbon, organic carbon and soil dust.…”

Aerosol distribution over Europe: a model evaluation study with detailed aerosol microphysics

“…Sectional aerosol models used in 3-D studies (e.g. Jacobson, 2001, Gong et al, 2003 reach generally a higher accuracy compared with the modal approach (Zhang et al, 1999) but are computationally more demanding. We have chosen the modal aerosol microphysical approach of M7 (Vignati et al, 2004) to extend the regional online climate-chemistry/aerosol model REMOTE (Langmann, 2000;.…”

GEM/POPs: a global 3-D dynamic model for semi-volatile persistent organic pollutants – Part 2: Global transports and budgets of PCBs

“…Due to the limited spatial and temporal resolutions of these models, a source-receptor relationship can hardly be inferred quantitatively for any specific geographical regions. Consequently, dynamical 3-D models have been developed to describe the atmospheric transport of POPs on both regional (Ma et al, 4016 P. Huang et al: Global transports and budgets of PCBs 2003;van Jaarsveld et al, 1997), hemispheric (Hansen et al, 2005;Malanichev et al, 2004) and global scales (Gong et al, 2007;Koziol and Pudykiewicz, 2001;Semeena and Lammel, 2005;Strand and Hov, 1996). Transport and deposition patterns of various POPs have been investigated with respect to factors such as the climate fluctuations.…”